id*  *.*  ' 


Cd^altimMa  llwixrjevsitg  ^^ 
in  tltc  crttij  0f  l^cxu  i;0r^ 

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Deaver.     Surgical   Anatomy. 

400  Full-page  Plates. 

A  Treatise  on  Human  Anatomy  in  its  Application  to  the  Practice  of 
Medicine  and  Surgery.  By  John  B.  Deaver,  m.d.,  Surgeon-in-chief 
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Morris.     Text-Book   of   Anatomy. 

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F.R.C.S.,  Arthur  Hexsman,  f.r.c.s.,  Frederick  Treves,  f.r.c.s., 
William  Anderson,  f.r.c.s.,  Arthur  Robinson,  m.d.,  m.r.c.s.,  and 
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THE 

DISSECTION   OF  THE  HUMAN   BODY 

HOLDEN 


GENERAL  TABLE  OF  CONTENTS. 


VOLUME    I. 

Scalp,  Face,  Orbit,  Neck, 
Thorax,  Upper  Extremity. 


VOLUME    II. 

Abdomen,  Lower  Extremity,  Brain,  Eye,  Organ  of 
Hearing,   Mammary  Gland,   Scrotum  and  Testis. 


Price  of  each  volume  in  uniform  bifiding,  $1.^0. 


By  the  Same  Author. 


HUMAN    OSTEOLOGY. 

Eighth  Edition,  with  Lithographic  Plates  and  Numerous 
Illustrations.      Bound  in  Cloth,  ^5.25. 


LANDMARKS,  MEDICAL   AND    SURGICAL. 

Fourth  Edition,  8  vo,  75  cents. 


HOLDEN'S   ANATOMY 

A   MANUAL   OF   THE 

DISSECTION  OF  THE  HUMAN   BODY 


y 


EDITED    BY 


JOHN    LANGTON 


SURGEON    TO,    AND    LECTURER    ON     ANATOMY    AT,    ST.    BARTHOLOMEW'S    HOSPITAL;     MEMBER     OF 

THE   BOARD   OF    EXAMINERS,    ROYAL    COLLEGE   OF    SURGEONS   OF    ENGLAND  ;    SURGEON 

TO    THE   CITY    OF    LONDON    TRUSS    SOCIETY  ;     CONSULTING    SURGEON     TO 

THE    CITY    OF     LONDON     LYING-IN    HOSPITAL    AND    TO    THE 

MEMORIAL    HOSPITAL    AT    MILDMAV     PARK. 


SEl/ENTH    EDITION 


REVISED    BY 

A.    HEWSON,    M.  D. 


DEMONSTRATOR     OF     ANATOMY,     JEFFERSON     MEDICAL     COLLEGE,     PHILADELPHIA  ;    SUUfiEON     TO 

ST.  timothy's    HOSPITAL;    DISPENSARY    SURGEON,  EPISCOPAL  HOSPITAL  ;    MEMBER 

ASSOCIATION     OF     AMERICAN     ANATOMISTS  :     FELLOW    OF 

THE    COLLEGE    OF    PHYSICIANS,    ETC. 


IN   TWO   VOLUMES 


VOLUME    1. 

SCALP,   FACE,  ORBIT,   NECK,   THORAX,   UPPER    EXTREMITY 

1^)  ILLUSTRATIONS 


PHILADELPHIA 
BLAKISTON'S    SON    &    CO. 
I0I2  WALNUT   STREET 
19OI 


Copyright,  I90I,by  P.  Blakiston's  Son  &  Co.,  Philadelphia. 


PREFACE  TO  THE  SEVENTH  EDITION 


In  this  edition  the  editor  lias  carefully  revised  the  entire 
work,  substituted  more  recent  cuts  for  older  ones,  and  added 
some  additional  matter  which  it  is  impossible  to  indicate  in  the 
text.  The  object  has  been  throughout  to  present  the  work 
thoroughly  adapted  for  the  use  of  the  students  in  the  dissecting 
room  and  for  reference  by  the  practitioner.  It  has  been  thought 
well,  for  the  convenience  of  the  former,  to  divide  the  book  into 
two  volumes.  The  total  number  of  cuts  has  not  been  materially 
increased,  but  se\'eral  new  ones  have  been  added  from  prepara- 
tions made  by  the  editor. 

A.  H. 

i_^oS  Pine  Street,  P/tiladelphia, 


347554 


PREFACE  TO  THE  SIXTH  EDITION. 


The  chief  feature  of  Holden's  Anatomy  that  rrmst  have 
become  apparent  to  all  who  have  hitherto  used  it,  is  not  only 
that  the  text  has  been  made  so  concise,  but  that  the  subject  is 
presented  in  as  clear  and  practical  a  light  as  is  compatible  with 
the  faithful  handling  of  its  natural  difficulties.  It  gives  to  the 
beginner  a  proper  method  of  procedure,  together  with  such  de- 
tails as  are  essential  to  the  thorough  understanding  of  the  matter 
in  hand.  In  making  this  revision  the  Editor  has  worked  in 
accc-rd  with  the  editors  of  the  previous  editions,  and  has  made 
such  additions  and  alterations  as  seemed  necessary  to  bring  the 
book  in  line  with  present  knowledge  and  methods,  and  has  added 
the  Metric  Measurements  side  by  side  with  the  English.  The 
entire  work  has  been  gone  over  line  for  line  ;  specially  empha- 
sized points  have  been  added  in  foot-notes  to  which  the  editor 
has  signed  his  initials  (A.  H.).  There  are,  however,  many 
additions  and  alterations  in  the  text  that  were  impossible  to  thus 
specify. 

It  has  seemed  well,  in  order  to  reduce  the  size  of  the  book 
and  still  retain  its  salient  features,  to  put  the  more  minute  and 
intricate  points  in  a  smaller  type.  This  will  be  found  an  aid  to 
the  student  and  has  allowed  of  the  addition  of  a  large  number 
of  new  illustrations. 

The  total  number  of  illustrations  has  been  increased  from 
208  to  311.  This,  however,  does  not  show  the  exact  number 
of  new  pictures,  as  many  of  those  that  appeared  in  the  old 
editions  have  been  struck  out  and  replaced  by  more  modern 
ones,  taken  chiefly  from  the  works  of  Sappey,  Wilson,  and 
Landois.  A,  H. 

IJ08  Pine  Street,  Philadelphia. 


PREFACE  TO  THE  FIRST  EDITION. 


If  any  apology  be  needed  for  the  appearance  of  the  present 
Manual,  it  may  be  stated,  without  any  wish  to  disparage  the 
labors  of  others,  that  the  works  of  this  kind  hitherto  published 
seem  to  the  Author  open  to  one  or  the  other  of  two  objections  ; 
—  either  as  being  too  systematic,  and  therefore  not  adapted  for 
the  dissecting-room,  or  as  obscuring  the  more  important  fea- 
tures of  Anatomy  by  a  multiplicity  of  minute  and  variable 
details. 

In  endeav'oring  to  supply  a  presumed  deficiency,  the  Author 
has  made  it  his  special  aim  to  direct  the  attention  of  the  student 
to  the  prominent  facts  of  Anatomy,  and  to  teach  him  the  ground- 
work of  the  science  ;  to  trace  the  connection,  and  to  point  out 
the  relative  situation  of  parts,  without  perplexing  him  with 
minute  descriptions. 

A  concise  and  accurate  account  is  given  of  all  the  parts  of 
the  human  body  —  the  bones  excepted,  of  which  a  competent 
knowledge  is  presupposed  —  and  directions  are  laid  down  for  the 
best  method  of  dissecting  it. 

The  several  regions  of  the  body  are  treated  of  in  the  order 
considered  most  suitable  for  their  examination  ;  and  the  muscles, 
vessels,  nerves,  etc.,  are  described  as  they  are  successively  ex 
posed  to  view  in  the  process  of  dissection. 

The  Author  has  written  the  work  entirely  from  actual  ob- 
servations :  at  the  same  time  no  available  sources  of  information 
have  been  neglected,  the  highest  authorities,  both  English  and 
Foreign,  have  been  carefully  consulted.  His  acknowledgments 
are  especially  due  to  F.  C.  Skev,  Esq.,  F.R.S.,  Lecturer  on 
Anatomy  at  St.  Bartholomew's  Hospital,  for  many  valuable  sug- 
gestions. Me  is  also  much  indebted  to  his  young  friend,  Mr.  W, 
Clubbe,  for  able  assistance  in  dissections, 

September,  /8ji. 


CONTENTS. 


PACK 

Dissection  of  the  Scalp, 19 

Dissection  of  the  Face, 40 

Dissection  of  the  Orbit, 63 

Dissection  of  the  Neck, 7^ 

Course  and  Relations  of  the  Subclavian  Arteries,  ....  127 
The  Muscles  of  Mastication.    Temporal  and  Pterygo-Maxil- 

lary  Regions, 140 

Branches  of  the  Internal  Maxillary  Artery  in  the  Three 

Stages  of  its  Course, 148 

Branches  of  the  Mandibular  Division  of  the  Fifth  Nerve,    .  151 

Dissection  of  the  Thorax, 167 

Dissection  of  the  Heart, 212 

Foetal  Circulation, 226 

Structure  of  the  Lungs, 227 

Dissection  of  the  Pharynx, 237 

Dissection  of  the  Larynx, 252 

Dissection  of  the  Tongue, 266 

Dissection  of  the  Maxillary  Nerve, 269 

Dissection  of  the  Ninth,  Tenth,  and  Eleventh  Cranial  Nerves  at 

the  Base  of  the  Skull, 274 

Dissection  of  the  Nose, 278 

Dissection  of  the  Muscles  of  the  Back, 284 

Ligaments  of  the  Spine, 296 

Dissection  of  the  Upper  Extremity, 307 

Dissection  of  the  Axilla, 313 

Dissection  of  the  Upper  Arm, 326 

Dissection  of  the  Front  of  the  Forearm, 340 

Dissection  of  the  Palm  of  the  Hand, 355 

Muscles  of  the  Back  connected  with  the  Arm, 367 

Dissection  of  the  Muscles  of  the  Shoulder,  _ 377 

Dissection  of  the  Back  of  the  Forearm, 3S6 

Dissection  of  the  Ligaments, 4°° 


LIST  OF  ILLUSTRATIONS. 


FIGURE  '  PAGE 

1.  Muscular  and  Aponeurotic  Stratum  of  the  Scalp, 20 

2.  Sensory  Nerves  of  the  Scalp  and  Face, 22 

3.  Branches  of  the  Facial  Nerve, 23 

4.  Section  of  Cranium,  showing  Falx  Cerebri, 27 

5.  Diagram  to  show  the  Formation  of  a  Sinus, 29 

6.  The  Cranial  Sinuses,       29 

7.  The  Venous  Sinuses  at  the  Base  of  the  Skull, 32 

8.  The  Exit  of  the  Cranial  Nerves, 35 

9.  The  Nerves  in  the  Foramen  Jugulare, 37 

10.  Relation  of  Structures  in  the  Cavernous  Sinus, 38 

11.  Relations  of  the  Nerves  in  tlie  Sphenoidal  Fissure, 38 

12.  Relations  of  the  Nerves  and  Muscles  in  the  Orbit, 39 

13.  The  Geniculate  Ganglion  of  the  Facial  Nerve, 39 

14.  The  Muscles  of  the  Face, 43 

15.  Tendon  of  the  Orbicularis  Palpebrarum, 44 

16.  Muscles  of  the  Eye, 48 

17.  The  Lachrymal  Apparatus, 49 

18.  Tensor  Tarsi, 50 

19.  Superficial  Muscles  of  the  Face  and  Neck, 51 

20.  The  Muscles  of  the  Pharynx, 53 

21.  The  Branches  of  the  External  Carotid  Artery, 55 

22.  Dissection  of  Face,  showing  Glands,       58 

23.  Nerves  of  the  Face, 61 

24.  The  Sensory  Nerves  of  the  Scalp  and  Face, 63 

25.  The  Nerves  of  the  Orbit, 65 

26.  View  of  the  Orbit  from  above, 67 

27.  Lachrymal  Gland, 68 

28.  Muscles  of  the  Eye, 69 

29.  View  of  the  Optic  and  Lower  Nerves  of  the  Orbit, 71 

30.  Diagram  of  the  Nerves  of  the  Orbit, 74 

31.  Insertion  of  the  Recti  Muscles, 75 

32.  The  Superficial  Nerves  and  Veins  of  the  Neck, 80 

33.  Cutaneous  Nerves  of  the  Neck, 83 

34.  Sterno-cleido-mastoid  Muscle  and  Muscles  above  and  below  the 

Hyoid  Bone, 86 

35.  The  Triangles  of  the  Neck, 88 

36.  Central  Line  of  the  Neck, 94 

37.  Muscles  of  the  Hyoid  and  Infra-hyoid  Regions, 95 

13 


14  I-IST    OF    ILLUSTRATIONS. 

PIGl'RB  PAGE 

38.  Relations  of  the  Carotid  Arteries, 97 

39.  Central  Line  of  Neck.  —  Cour.se  and  Relations  of  Common  Carotid 

Artery,       100 

40.  Lymphatic  Vessels  Coming  from  the   Glands   of  the    Neck   and 

Axilla, 104 

41.  Digastric  Triangle  and  Contents, 107 

42.  Central  Line  of  Neck.  —  Course  and  Relations  of  Common  Carotid 

Artery, ' 112 

43.  The  Branches  of  the  External  Carotid  Artery  and  their  Branches,  113 

44.  Gasserian  Ganglion  and  Branches, 114 

45.  Muscles,  Vessels,  and  Nerves  of  the  Tongue, 117 

46.  Scalene  Muscles, 126 

47.  The  Heart  and  Large  Vessels, 129 

48.  Lymphatic  \'essels  Coming  from   the   Glands  of   the  Neck   and 

Axilla, 131 

49.  Branches  of  the  Subclavian  Artery, 133 

50.  The  Inosculations  of  the  Subclavian  Artery, 137 

51.  The  Formation  of  the  Brachial  Plexus  and  its  Branches,   ....  139 

52.  Dissection  of  Face,  showing  Glands, 141 

53.  Temporal  Muscle, 144 

54.  Pterygoid  Muscles  and  the  Internal  Maxillary  Artery, 146 

55.  External  Carotid  Artery  and  its  Branches, 148 

56.  Plan  of  the  Internal  Maxillary  Artery, 149 

57.  Gasserian  Ganglion  and  Branches, 152 

58.  Muscles  of  Tongue  and  Glottis, 156 

59.  Origin  and  Distribution  of  the  Glosso-Pharyngeal,  Pneumogastric, 

and  Spinal  Accessory  Nerves, 161 

60.  The  Communications  of  the  Facial,  Glosso-pharyngeal,  Pneumogas- 

tric, Spinal  Acce.ssory,  Hypoglossal,  Sympathetic,  and  the  two 

Upper  Cervial  Nerves, 166 

61.  Showing  Position  of  the  Heart  and  its  Valves  in  Relation  to  the 

Chest  Walls, 170 

62.  The  Reflections  of  the  Pleural  Sacs, 173 

63.  .Showing  Interpleural  Space, 175 

64.  Form  and  Position  of  the  Lungs, 177 

65.  Anterior  View  of  the  Thorax, 179 

66.  Relative  Position  of  the  Heart  and  its  Valves  with  regard  to  the 

Walls  of  the  Chest, 181 

67.  Ventral  Topography  of  Viscera  of  the  Throat  and  Abdomen     .     .  184 

68.  Dorsal  Topography  of  Viscera  of  the  Throat  and  Abdomen  ...  185 

69.  Right  Lateral  Topography  of  Viscera  of  the  Throat  and  Abdomen  187 

70.  Left  Lateral  Topography  of  Viscera  of  the  Throat  and  Abdomen  1S8 

71.  Relation  of  the  Pericardium, 188 

72.  Superior  Vena  Cava  and  its  Tributaries, 191 

73.  Course  and  Relations  of  the  Arch  and  the  Aorta, 193 

74.  The  Course  of  the  Vena  Azygos  and  the  Thoracic  Duct,   ....  199 


LIST    OF    ILLUSTRATIONS.  15 

FIGURE  PAGE 

75.  The  Thoracic  Portion  of  the  Sympathetic  Nerve, 205 

76.  Diagram  of  a  Spinal  Nerve, 208 

77.  The  Constituents  of   the  Root  of   each  Lung  and  their  Relative 

Position, 211 

78.  The  Interior  of  the  Right  Auricle, 215 

79.  Anatomy  of  the  Hea.t— Right  Side, 218 

80.  Anatomy  of  the  Heart  —  Left  Side, 219 

81.  The   Relative    Position   of   the  Valves  of   the  Heart  seen   from 

above, 224 

82.  Scheme  of  the  Foetal  Circulation, 226 

83.  Anterior  View  of  the  Larynx, 229 

84.  Anterior  View  of  the  Thorax, 231 

85.  Ultimate  Air-cells  of  the  Lung, 235 

86.  Side  View  of  the  Muscles  of  the  Pharynx, 239 

87.  View  of  the  Constrictor  Muscles  from  behind, 241 

88.  View  of  the  Pharynx  laid  open  from  behind, 244 

89.  Pharynx  opened  Posteriorly, 247 

90.  Vertical  Section  of  the  Nasal  Fossae  and  Mouth, 249 

91.  Anterior  View  of  Os  Hyoides, 253 

92.  Larynx,  Front  View,  with  the  Ligaments  and  Insertion  of  Muscles,  255 

93.  Posterior  View  of  the  Larynx,  with  the  Muscles  Removed,  .     .     .  255 

94.  Shape  of  the  Glottis  when  at  rest, 259 

95.  Posterior  View  of  the  Larynx,  with  its  Muscles, 260 

96.  Diagram  showing  the  Action  of  the  Crico-thyroid  Muscle,  .     .     .  261 

97.  Glottis  dilated  :  Muscles  dilating  it, 261 

98.  Side  view  of  the  Muscles  of  the  Larynx, 262 

99.  Glottis  closed  :  Muscles  closing  it, 263 

100.  Nerves  of  the  Larynx, 264 

loi.  Upper  Surface  of  the  Tongue,  with  the  Fauces  and  Tonsils,    ,     .  267 

102.  Diagram  of  the  Maxillary  Nerve, 270 

103.  Maxilliary  Nerve  seen  from  without, 271 

104.  Communications  of  the  Facial,  Glosso-pharyngeal,  Pneumogas- 

tric.  Spinal  Accessory,  Hypoglossal,  Sympathetic,  and  the  two 

Upper  Cervical  Nerves, 273 

105.  The  Geniculate  Ganglion  of  the  Facial  Nerve  and  its  Connections,  276 

106.  Cartilages  of  the  Nose, 270 

107.  Vertical  Section  of  the  Nasal  Fo-ssae  and  Mouth, 281 

108.  Transverse  Section  of  the  Nasal  Fossje, 282 

109.  Transverse  Section  through  the  Abdomen  to  show  the  attach- 

ment of  the  Lumbar  Fascia 28<; 

no.  The  Superficial  Muscles  of  the  Back, 286 

111.  The  Suboccipital  Triangle .291 

112.  The  Cutaneous  Nerves  of  the  Back, 293 

113.  The  Prevertebral  Muscles '295 

114.  Occipito-Cervical  Ligament, ^01 

115.  Vertical  Transverse  Section  of  Spinal  Column  and  the  Occipital 

Bone  to  show  Ligaments, ^q, 

116.  Costo-vertebral  Ligaments, ^^^ 


1 6  LIST    OF    ILLUSTRATIONS. 

FICIRE  PAGE 

17.  The  Ligaments  connecting  the  Rib  with  the  Vetebra, 304 

iS.  Transverse  Section  to  show  the  Ligaments  and  the  Fibro-Carti- 

lage  of  the  Lower  Jaw, 305 

19.  Thoracfc  and  Brachial   Lymphatic  Vessels  emptying  into  the 

Axillary  Lymphatic  Glands, 315 

20.  Muscles  of  the  Anterior  Part  of  the  Thorax, 316 

21.  The  Axilla 318 

22.  Plan  of  the  Branches  of  the  Axillary  Artery, 319 

23.  The  Origins  of  the  Triceps, 319 

24.  The  Brachial  Plexus  of  Nerves 321 

25.  Muscles  of  the  Back  (Superficial), 324 

26.  Distribution  of  the  Cutaneous  JSferves  to  the  front  of  the  Shoulder 

and  Arm, 326 

27.  Superficial  Veins  and  Nerves  at  the  Bend  of  the  Left  Elbow,  .     .  327 

28.  Anterior  Muscles  of  the  Arm,       . 331 

29.  Plan  of  the  Chief  Branches  of  the  Brachial  Artery, 334 

30.  Brachial  Portion  of  Musculo-Cutaneous  Median  andUlnar  Nerves,  337 

31.  Terminal  Portion  of  the  Median  and  LHnar  Nerves, 337 

32.  Triceps  Muscle, 339 

^^.  Superficial  Muscles  on  the  Anterior  Surface  of  the  Left  Forearm,  344 

34.  Flexor  Muscles  of  the  Fingers, 346 

35.  Terminal  Branches  of  the  Radial  Nerve, 350 

36.  Deep  Flexor  of  the  Fingers, 354 

37.  Diagram  of  the  Superficial  and  Deep  Palmar  Arches,      ....  358 

38.  Cutaneous  Nerves  of  the  Back, 369 

39.  The  Superficial  Muscles  of  the  Back, 371 

40.  Cutaneous  Nerves  of  the  Left  Shoulder  and  Arm  (posterior  view),  378 

41.  Analysis  of  the  Deltoid, 379 

42.  Triceps  Muscle, 380 

43.  Anterior  Muscles  of  the  Arm, 380 

44.  The  Arteries  of  the  Scapula, 384 

45.  Superficial  Extensors  of  the  Forearm ,     .     .     .     .  389 

46.  Deep  Extensors  of  the  Forearm, 394 

47.  The  Anastomoses  of  the  Arteries  at  the  back  of  the  Elbow  and 

Wrist  Joints, 396 

48.  The  Dorsal  Interossei, 399 

49.  The  Palmar  Interossei,  and  the  Adductor  Pollicis, 399 

50.  The  Sterno-clavicular  Ligaments, 401 

51.  Anterior  view  of   the  Scapulo-clavicular  Ligaments,  and  of   the 

Shoulder-joint, 403 

52.  Ligaments  of  the  Elbow-joint 407 

53.  The  Ligaments  and  Synovial  Membranes  of  the  Wrist-joint,     .     .  410 


A   MANUAL 

OF   THE 

Dissection  of  the  Human  Body. 


DISSECTION    OF   THE    SCALP. 

Dissection.  —  An  incision  should  be  made  from  the  root  of 
the  nose  {nasion)  along  the  mesial  line  of  the  vertex  to  the  ex- 
ternal protuberance  of  the  occipital  bone  {inion)  ;  another  hori- 
zontally round  each  half  of  the  head,  to  join  at  right  angles  the 
two  ends  of  the  first  incision.  These  incisions  must  not  divide 
more  than  the  skin,  so  that  the  subcutaneous  vessels  and  nerves 
be  not  injured.  It  is  well  to  dissect  on  one  side  of  the  head  the 
muscles  only,  reserving  the  other  side  for  the  dissection  of  the 
vessels  and  nerves. 

Strata  Composing  the  Scalp The  several  strata  of  tis- 
sues covering  the  skull-cap  are —  i,  the  skin  ;  2,  a  thin  layer  of 
connective  tissue  and  fat  which  contains  the  cutaneous  vessels 
and  nerves  and  the  bulbs  of  the  hair ;  and  by  which  the  skin  is 
very  closely  connected  to,  3,  the  broad  tJmi  apo7iciirosis  of  the 
occipito-fontalis  muscle  (aponeurosis  of  the  scalp)  ;  4,  an  abun- 
dance of  loose  connective  tissue,  which  permits  the  free  motion 
of  the  scalp  upon,  5,  \hQ  pericranium,  or  periosteum  of  the  skull- 
cap. 

Immediately  beneath  the  skin,  we  expose  the  thin  stratum 
of  connective  and  adipose  tissue  which  firmly  connects  it  with 
the  aponeurosis  of  the  scalp.  This  layer  is  continuous  behind 
with  the  superficial  fascia  covering  the  muscles  at  the  back  of 
the  neck,  and  laterally  it  passes  over  the  temporal  fascia.  It 
forms  a  bed  for  the  bulbs  of  the  hair  and  for  the  ramifications  of 
the  cutaneous  arteries.  The  toughness  of  this  tissue,  in  which 
the  arteries  ramify,  does  not  permit  them  to  retract  when  divided ; 
hence  the  haemorrhage  which    follows   incised   wounds   of   the 

19 


20 


DISEASES    OF    THE    SCALP. 


scalp  ;  hence  also  the  difficulty  of  drawing  them  out  with  the 
forceps. 

Occipito-frontalis  Muscle  and  Epicranial  Aponeurosis 

This  cutaneous  muscle  is  closely  connected  to  the  scalp.  It 
consists  of  two  fleshy  portions,  one  on  the  occiput,  the  other  on 
the  forehead,  connected  by  a  broad  aponeurosis.  Ihe  occipital 
portion  of  the  muscle  is  thin,  and  takes  origin  from  the  outer 
two-thirds  of  the  upper  curved  line  of  the  occipital  bone,  and  the 
adjoining  part  of  the  mastoid  process  of  the  temporal  bone.     The 


Fig.  I.  —  Diagram   Showing   the   Muscular  and   Aponeurotic   Stratum   of  the   Scalp. 
A.  Attollens  aurem.     b.  Attrahens  aurem.     c.  Retrahens  aurem.     d.    Orbicularis  palpebrarum. 


fibres  ascend  over  the  back  of  the  head  for  about  two  inches, 
and  then  terminate  in  the  epicranial  aponeurosis.  The  frontal 
portion,  commencing  in  an  arched  form  from  the  epicranial  apo- 
neurosis below  the  coronal  suture,  descends  over  the  forehead, 
and  terminates  partly  in  the  skin  of  the  brow,  partly  in  the  orbi- 
cularis oculi  and  corrugator  and  supercilii,  while  some  of  the 
inner  fibres  are  continuous  in  front  of  the  nose  with  the  pyra- 
midalis  nasi  muscle.  The  aponeurosis  of  the  scalp  covers  the 
vertex  of  the  skull,  the  two  being  continuous  across  the  middle 
line.     It  is  continued  over  the  temples  and  side  of  the  head, 


ARTERIES    OF   SCALP.  21 

gradually  changing  from  tendinous  into  connective  tissue.  This 
muscle  enables  us  to  move  the  scalp  backwards  and  forwards. 
But  its  chief  action  is  as  a  muscle  of  expression.  It  elevates 
the  brows,  and  occasions  the  transverse  wrinkles  in  the  expres- 
sion of  surprise. 

The  occipital  portion  is  supplied  by  the  posterior  auricular  branch  of  the  facial ; 
the  frontal  portion  by  the  temporal  branch  of  the  same  nerve.  , 

Muscles  of  the  Ear. — There  are  several  small  muscles  to 
move  the  cartilage  of  the  ear.  In  man  they  are  thin  and  pale, 
and  require  care  to  dissect  them  out  satisfactorily.  In  animals, 
who  possess  a  more  delicate  sense  of  hearing,  they  are  much 
more  developed,  for  the  purpose  of  quickly  directing  the  carti- 
lage of  the  ear  towards  the  direction  of  the  sound. 

Attollens  Aurem To  indicate  the  position  of  this  muscle 

the  student  should  draw  down  the  upper  part  of  the  pinna  of 
the  ear,  when  it  will  be  found  immediately  under  the  ridge  of 
skin  so  produced.  It  is  a  thin,  fan-shaped  muscle  and  atises 
from  the  epicranial  aponeurosis,  and  is  inserted  into  the  cranial 
aspect  of  the  upper  part  of  the  concha. 

Attrahens  Aurem. — -This  muscle  is  the  smallest  of  these 
muscles,  and  its  situation  is  indicated  by  the  prominence  of  skin 
produced  by  drawing  backwards  the  front  part  of  the  helix,  or 
outer  rim  of  the  cartilage  of  the  ear.  It  anses  from  the  apo- 
neurosis of  the  occipito-frontalis,  and  is  inserted  into  the  front 
of  the  helix. 

Retrahens  Aurem This  muscle  is  exposed  by  reflecting 

the  skin  from  the  ridge  produced  by  drawing  the  pinna  for- 
wards. Consisting  of  two  or  three  fasciculi,  it  arises  from  the 
base  of  the  mastoid  process  and  is  inserted  into  the  lower  part 
of  the  concha,  or  expanded  portion  of  the  cartilaginous  auditory 
canal. 

The  retrahens  and  the  attollens  aurem  are  supplied  by  the  posterior  auricular 
branch  of  the  facial  nerve ;  the  attrahens,  by  an  offset  from  the  temporal  branch 
of  the  same  nerve. 

Arteries  of  Scalp The  arteries  of  the  scalp  are  derived,  in 

front,  from  the  supra-orbital  and  frontal  arteries,  branches  of 
the  ophthalmic  artery,  which  is  a  branch  of  the  internal  carotid  ; 
on  the  sides,  from  the  temporal ;  behind  from  the  occipital  and 
posterior  aiiriciilar,  all  branches  of  the  external  carotid. 

The  frontal  emerges  from  the  orbit  at  its  inner  angle ;  it  runs  upwards  for  a 
short  distance  on  the  forehead  and  inosculates  -with  the  following  artery. 

The  supra-orbital  passes  through  the  supra  orbital  notch  and  then  divides  into 


22  NERVES    OF    THE    SCALP. 

a  superficial  and  a  deep  branch.  It  distributes  branches,  some  of  which  ascend 
toward  the  top  of  the  head  and  communicate  with  the  temporal  and  frontal 
arteries. 

The  temporal,  about  two  inches  above  the  zygoma,  divides  into  two  branches  — 
an  anterior  and  a  posterior.  The  anterior  runs  forwards  in  a  tortuous  course  and 
anastomoses  with  the  supra-orbital  and  frontal  arteries ;  the  posterior  (usually  the 
larger)  arches  backwards  over  the  temporal  fascia,  and  its  branches  communicate 
with  the  corresponding  branch  of  the  opposite  side  and  with  the  occipital  and 
posterior  auncular  arteries. 

The  posterior  auricular  is  a  small  vessel  seen  in  the  cleft  between  the  ear  and 
the  mastoid  process.  It  ascends,  and  divides  into  two  branches  :  one,  the  maltoid 
or  occipital,  which  passes  backwards  and  inosculates  with  the  occipital ;  the  other, 
the  auricular,  which  runs  forwards  above  the  ear  and  communicates  with  the  poste- 
rior branch  of  the  temporal  artery. 

The  occipital  may  be  noticed  piercing  the  trapezius  near  to  the  external  occi- 
pital protuberance ;  ascending  over  the  back  of  the  head,  it  divides  into  numerous 
branches  which  inosculate  with  the  preceding  arteries. 


Fig.  2.  —  Diagram  of  the  Sensory  Nerves  of  the  Scalp  and  Face. 


Great  occipital.  2.  Small  occipital.  3.  Auricular  br.  of  the  pneumogastric.  4.  Great  auri- 
cular. 5.  Auriculotemporal.  6.  Temporal  br.  of  maxillary  nerve.  7.  Supra-orbital.  8.  Supra- 
trochlear. 9.  Malar  br.  of  maxillary  nerve.  10.  Infra-trochlear.  11.  Nasolobular.  12.  Infra- 
orbital.    13.  Buccal  br.  of  mandibular  nerve.     14.  Mental. 


The  frontal  vein  passes  downwards  with  its  corresponding 
artery,  and  joins  the  supra-orbital  vein,  to  form  the  angular  vein. 
The  other  veins  of  the  scalp  accompany  their  respective  arteries. 

Nerves  of  the  Scalp.  —  The  sensory  nerves  of  the  scalp  are 
derived  from  each  of  the  three  divisions  of  the  fifth  cranial 
nerve  —  namely,  the  ophthalmic,  the  maxillary  and  mandibu- 
lar ;  also  from  the  second  cervical  nerve.     The  nerves  to  the 


NERVES    OF    THE    SCALP. 


23 


muscles  of  the  scalp  and  ear  come  from  the  facial  seventh  cranial 
nerve. 

In  front  will  be  found  the  supra-trochlear  and  supra-orbital 
nerves ;  in  the  temporal  region,  there  are  the  temporal  fila- 
ment from  the  orbital  branch  of  the  maxillary,  the  auriculo- 
temporal, and  the  temporal  branches  of  the  facial  nerve  ;  and 
behind  will  be  seen  the  posterior  auricular  branch  of  the  facial, 
the  small  and  great  occipital  nerves,  and  occasionally  a  small 
filament  from  the  posterior  division  of  the  sub-occipital  nerve. 

The  supratrochlear  neri'e  is  derived  from  the  frontal  branch  of  the  ophthalmic 
division  of  the  fifth.  It  appears  at  the  inner  angle  of  the  orbit,  and  ascending 
beneath  the  orbicularis  palpebrarum  and  occipito-frontalis,  it  finally  supplies  the 
skin  of  the  forehead  and  the  upper  eyelid. 


Fig.  3.  —  Diagram  of  the  Branches  of  the  Facial  Nerve. 
Branch  to  occipito-frontalis.     2.  Posterior  auricular.     3.  Temporal  brs.    4.  Malar  brs.     5.  Infra- 
orbital.    6.  Buccal.     7.  Supra-maxillary.     8.  Infra-maxillary. 


The  mpraorhital  nerve  is  a  continuation  of  the  frontal  branch  of  the  fifth.  It 
emerges  from  the  orbit  through  the  notch  in  the  frontal  bone,  and  subdivides  into 
branches,  which  are  covered  at  first  by  the  fibres  of  the  orbicularis  and  occipito- 
frontalis;  but  they  presently  become  subcutaneous,  and  terminate  in  two  branches 
—  an  inner,  which  ascends,  to  supply  the  structures  as  high  as  the  parietal  bone; 
and  an  outer  and  larger,  which  may  be  traced  over  the  verte.x  as  far  as  the  occipital 
bone. 

The  temporal  branch  of  the  orbital  branch  of  the  maxillary  nerve  pierces  the 
temporal  fascia  about  an  inch  above  the  zygoma  and  is  distributed  to  the  skin 
of  the  temple,  communicating  with  the  facial  nerve  and  occasionally  with  the  fol- 
lowing. 

The  auriculotemporal  nerve,  a  branch  of  the  mandibular  nerve,  after  sending 


24  NERVES    OF    THE    SCALP. 

a  small  filament  to  the  upper  part  of  the  pinna,  divides  into  two  branches  which 
accompany  the  divisions  of  the  superficial  temporal  artery  ;  of  these,  the  posterior 
is  the  smaller.  The  anterior  communicates  with  the  facial  nerve,  and  with  the 
orbital  branch  of  the  maxillary. 

The  temporal  branches  of  the  facial  nerve  lie  superficial  to  the  temporal  fascia, 
and  supply  the  attrahens  and  attollens  aurem,  the  orbicularis  palpebrarum,  the  cor- 
rugator  supercilii,  and  the  occipito-frontalis.  These  branches  communicate  with 
the  temporal  bianch  of  the  maxillary,  the  auriculo-lemporal  nerve,  and  with  the 
lacrymal  and  supra-orbital  branches  of  the  ophthalmic. 

The  posterior  auricular  nerve  is  a  branch  of  the  facial,  and  divides  like  its 
accompanying  artery  behind  the  pinna  of  the  ear  into  a  posterior  or  occipital 
branch  which  supplies  the  posterior  belly  of  the  occipito-frontalis,  and  into  an 
anterior  or  auricular  branch  which  ends  in  the  auricle,  the  retrahens,  and  attollens 
aurem.  It  communicates  with  the  great  auricular  and  small  occipital  nerves,  and 
with  the  auricular  branch  (Arnold's)  of  the  pneumogastric. 

The  auricular  bra>ich  of  the  pneumogastric  (Arnold's)  emerges  from  the  auricular 
fissure  immediately  behind  the  pinna,  and  supplies  the  skin  of  the  pinna  and  the 
neighborhood. 

The  great  occipital  nerve  is  the  internal  branch  of  the  posterior  division  of  the 
second  cervical  nerve.  After  piercing  the  complexus  it  appears  on  the  occiput 
with  the  occipital  artery,  and  divides  into  wide-spreading  branches  which  supply 
the  skin.  It  communicates  with  the  posterior  auricular,  the  small  occipital,  and 
the  third  cervical  nerves. 

The  small  occipital  nerve,  a  branch  of  the  anterior  division  of  the  second  cer- 
vical nerve,  runs  along  the  posterior  border  of  the  sterno-niastoid  and  supplies  the 
scalp  behind  the  ear.  It  communicates  with  the  great  auricular,  and  with  the  two 
preceding  nerves. 

Occasionally,  though  rarely,  a  cutaneous  branch  of  the  suboccipital  }ierve  is  dis- 
tributed to  the  back  of  the  head. 

Lymphatics  of  the  Scalp.  —  The  lymphatics  of  the  scalp  run  for  the  most  part 
backwards  towards  the  occiput  to  join  the  occipital  and  posterior  auricular  glands; 
a  few  run  towards  the  root  of  the  zygoma,  where  they  enter  the  parotid  lymphatic 
glands.  It  is  in  these  situations,  therefore,  that  one  finds  glandular  enlargements 
when  the  scalp  is  diseased. 

Points  of  Surgical  Interest.  —  Raise  the  aponeurosis  of  the 
scalp,  and  observe  the  quantity  of  loose  connective  tissue  which 
intervenes  between  it  and  the  pericranium.  This  tissue  never 
contains  fat.  There  are  some  points  of  surgical  interest  con- 
cerning it  :  I.  Its  looseness  accounts  for  the  extensive  effusions 
of  blood  which  one  often  sees  after  injuries  of  the  head.  2.  It 
admits  of  large  flaps  of  the  scalp  being  detached  from  the  skull- 
cap ;  but  these  flaps  rarely  slough,  unless  severely  damaged, 
because  they  carry  their  blood-vessels  with  them.  In  phlegmo- 
nous erysipelas  of  the  scalp,  the  connected  tissue  becomes  infil- 
trated with  pus  and  sloughs  ;  hence  the  necessity  of  making 
incisions  ;  for  the  scalp  will  not  lose  its  vitality  and  liberate  the 
sloughs,  like  the  skin  of  other  parts  under  similar  conditions, 
because  its  vessels  run  above  the  diseased  tissue,  and  therefore 
its  supply  of  blood  is  not  cut  off. 

The  alveolar  point.  —  The  centre  of  the  ventral  surface  of  the  alveolar  arch. 
The  aiterion  (icrri^p,  a  star).  —  The  star-shaped  suture  made  by  the  junction 


NERV^ES    OF    THE    SCALP.  2$ 

of  the  mastoid  portion  of  the  temporal,  the  occipital,  and  post  inferior  angle  of  the 
parietal  bones.  It  may  be  measured  from  the  auricular  point  on  a  line  continuous 
with  the  cephalad  margin  of  the  zygoma  about  two  inches  (5  cm.).  It  indicates 
the  position  of  the  e.xtreme  lateral  portion,  the  lateral  sinus,  and  the  commence- 
ment of  the  sigmoid  portion  of  the  same.  A  line  drawn  vertical  from  the  asterion 
one  inch  (2.5  cm.)  locates  the  entrance  of  the  mastoid  vein  when  present. 

The  basion  (/Sicrtj,  a  base).  —  The  centre  of  the  ventral  or  anterior  margin  of 
the  foramen  magnum.  A  line  drawn  horizontally  bisects  each  bony  external 
auditory  meatus,  or  aiiricidar  point. 

The  bregma  {^piyiM,  from  pp^xeiv,  to  moisten,  being  the  soft  part  of  the  infant 
skull).  —  The  point  of  union  of  the  interparietal  and  fronto-parietal  sutures. 

The  glabella  (glabellus,  without  hair).  —  A  prominence  (sometimes  a  depres- 
sion) above  the  nasion,  between  the  superciliary  ridges,  corresponding  to  the  basal 
surface  of  the  frontal  cerebral  lobes. 

The  inion  (ivlov,  the  occiput).  —  The  external  occipital  protuberance.  It  is 
below  the  occipital  point,  and  is  consequently  nearer  to  the  glabella  in  the  trans- 
cephalic  measurement. 

The  lambda  (from  the  Greek  letter  A).  —  The  junction  of  interparietal  and  the 
parietooccipital  sutures. 

The  nasion  (nasus,  the  nose).  —  Mid  point  of  junction  of  internasal  and  naso- 
frontal sutures. 

The  obelion  (o/SeXis,  a  spit). —  Being  the  point  of  intersection  of  the  sagittal 
suture  and  a  line  through  the  parietal  foramen. 

The  occipital  point.  —  That  point  on  the  median  of  the  occiput  line  farthest 
removed  from  the  glabella. 

The  ophryon  [dcpp'u's,  the  eyebrow)  or  supra  orbital  point.  —  The  centre  of  a  line 
drawn  transversely  at  the  narrowest  portion  of  the  forehead,  being  the  line  of 
separation  between  cranium  and  face. 

The  opisthion  (6ir lard  1.0s,  hinder).  —  The  centre  of  dorsal  or  posterior  margin  of 
the  foramen  magnum.  A  line  drawn  horizontally  at  this  point,  and  another  bisect- 
ing the  emenentia  articularis  marks  the  limits  of  the  sub-cranial  region.  That 
portion  posterior  or  dorsal  to  the  opisthionic  line  bisects  the  sub-occipital  region. 

The  pterion  {irripov,  a  wing).  — The  H-shaped  suture  made  by  the  junction  of 
the  frontal,  temporal,  parietal,  and  the  temporal  fossa  surface  of  the  great  wing  of 
the  sphenoid  bones.  It  may  be  located  on  a  Une  drawn  parallel  to  the  zygomatic 
arch  from  the  external  angular  process  of  the  frontal  bone.  It  is  about  one  and 
one-half  to  two  inches  from  the  angular  process,  and  the  same  distance  from  the 
centre  of  the  upper  or  cephalad  margin  of  the  zygoma.  It  is  of  surgical  impor- 
tance from  the  relation  of  the  anterior  trunk  of  the  large  meningeal  artery  passmg 
obliquely  from  below  upward  (caudo-cephelad)  between  the  ventral  and  dorsal 
portion  of  this  suture.  The  separation  between  the  basal  portion  of  the  frontal 
lobe  and  the  superior  or  cephalad  portion  of  the  tempero-sphenoidal  lobe.  It  also 
marks  the  division  of  the  fissure  of  Sylvius  into  its  vertical  and  horizontal  por- 
tions. There  is  often  a  sesamoid  bone  situated  here,  the  epipteric  bone  of  Flower, 
which  may  be  mistaken  for  a  fracture. 

The  Stephanion  (sT€<t>dviov,  dim.  of  arecpivos,  a  crown),  —  The  point  where  the 
temporal  ridge  crosses  the  fronto-parietal  suture.  The  anterior  or  ventral  branch 
of  the  anterior  dural  artery  is  usual  at  this  point.  The  inferior  frontal  sulcus 
is  also  in  close  proximity. 

Circumference  of  the  skull  should  be  made  in  a  plane  passing  from  the  ophryon 
to  the  occipital  point.  The  maximum  cranial  length  is  measured  from  the  most 
prominent  portion  of  the  glabella  to  the  occipital  point.  The  maximum  breadth  is 
the  greatest  transverse  diameter  of  the  cranium  measured  above  the  supramastoid 

ridge  to  the  median  plane.     The  cephalic  index  is  therefore  I 1.    The 

height  of  the  cranium  is  measured  from  the  basion  to  the  bregma.     The  index  of 
height  is  less  subject  to  variation  than  the  breadth-index. 


26  DURA. 

The  stib-nasal. — The  centre  of  the  caudal  or  inferior  border  of  the  ventral  or 
anterior  nares,  being  at  the  base  of  the  spine. 

If  the  skin  has  been  removed  from  the  face  in  dissecting  its  nerves,  the  student 
is  advised  to  continue  the  facial  dissection,  as  in  well-injected  subjects  the  brain 
will  keep  well  in  the  skull. 

Dissection.  —  To  examine  the  brain  and  its  membranes,  the 
skull-cap  must  be  removed  about  half  an  inch  above  the  supra- 
orbital ridges  in  front,  and  on  a  level  with  the  occipital  protu- 
berance behind.  The  student  should  remember  that  the  bone 
in  the  temporal  region  is  very  thin,  and  that  here  especial  care 
is  needed  that  the  brain  be  not  injured  by  the  saw.  It  is  bet- 
ter to  saw  only  through  the  outer  table  of  the  skull,  and  to 
break  through  the  inner  with  a  chisel.  In  this  way  the  dura 
and  the  brain  are  less  likely  to  be  injured.  On  removing  the 
skull-cap,  which  is  more  or  less  intimately  attached  to  the  sub- 
jacent membrane,  we  expose  a  tough  fibrous  layer,  the  dura, 
which  forms  the  most  external  of  the  membranes  of  the  brain. 

The  meningeal  or  dural  arteries  ramify  between  the  skull  and 
the  dura.  We  cannot,  however,  with  the  brain  in  sitti,  trace 
their  course,  at  present,  throughout  ;  so  their  consideration  must 
be  deferred  until  the  brain  has  been  removed. 

Dura.*  —  This  membrane  is  a  dense  white  fibrous  membrane, 
rough  on  its  outer  aspect,  where  it  is  more  or  less  adherent 
to  the  inner  surface  of  the  skull,  forming  its  internal  periosteum. 
On  its  inner  surface  it  is  smooth  and  shining,  being  lined  by 
a  layer  of  endothelial  cells,  which  anatomists  now  describe  as 
constituting  a  part  of  the  dura.  In  consequence,  the  term 
''  subdural  space"  is  now  substituted  for  the  old  one — ''the 
cavity  of  the  arachnoid."  The  dura  differs  in  its  adhesion 
to  the  subjacent  bones  :  its  adhesion  is  firmest  at  the  sutures, 
the  petrous  portion  of  the  temporal  bone,  the  basilar  process, 
the  body  of  the  sphenoid,  the  cribriform  plate  of  the  ethmoid 
bone,  the  depressions  for  the  Pacchionian  bodies,  and  at  the 
margin  of  the  foramen  magnum.  In  front  it  sends  downwards 
a  prolongation  into  the  foramen  c^cum  ;  also  numerous  small 
tubular  .sheaths  through  the  foramina  in  the  cribriform  plate. 
It  further  sends  a  prolongation  through  the  optic  foramen,  and 
another  through  the  sphenoidal  fissure  into  the  orbit. 

The  dura  is  supplied  with  nerrcs  by  the  recurrent  branch  of  the  fourth  ner\'e, 
and  by  the  .ifth  cranial  nerve.  Filaments  have  likewise  been  traced  into  it  from 
the  sympathetic  and  from  the  Gasserian  ganglion. 

*  The  dura  is  divided  into  two  inseparable  layers.  The  outer  or  periosteal 
lamina  and  an  inner  of  supporting  lamina.  It  is  to  the  latter  lamina  that  sinuses 
owe  their  formalicxn  for  the  most  part. 


DURA. 


27 


Its  remarkably  tough  and  fibrous  structure  adapts  it  exceed- 
ingly well  to  the  four  purposes  which  it  serves  :  i.  It  forms  the 
internal  periosteum  of  the  skull.  2.  It  forms,  for  the  support 
of  the  lobes  of  the  brain,  three  partitions  —  namely,  the  falx, 
the  falcula,  and  the  tentorium.*  3.  It  forms  the  sinuses  or 
venous  canals  which  return  the  blood  from  the  brain.  4.  It 
forms  sheaths  for  the  nerves  as  they  leave  the  skull. 


Fig  4 
I.  Falx  2,  2  Its  convex  border  enclosing  the  superior  longitudinal  sinus.  .  Its  concave  border. 
4,  4  Inferior  longitudinal  sinub.  5  Base  of  the  falx.  6.  Straight  sinus.  7.  Apex  of  the  falx 
attached  to  the  crista  galli.  8.  Right  half  of  the  tentorium  from  the  interior  surface,  q.  Right 
lateral  sinus.  10.  Superior  petrosal  sinus.  11.  Inferior  petrosal  sinus.  12.  Occipital  sinus. 
13.  Falcula.  14.  Optic  or  second  nerve.  15.  Third  nerve.  16.  Fourth  nerve.  17.  Fifth  nerve. 
18.  Sixth  nerve,  ig.  Seventh  and  eighth  nerves.  20.  Ninth,  tenth,  and  eleventh  nerves.  21. 
Twelfth  nerve.  22.  First  pair  of  cervical  nerves.  23.  Second  pair  of  cervical  nerves.  24.  Su- 
perior end  of  linamentum  denticulatum.     25.  Venae  Galeni. 

Of  the  partitions  formed  by  the  dura  for  the  support  of  the 
lobes  of  the  brain,  two  are  vertical,  and  separate,  respectively, 
the  two  hemispheres  of  the  cerebrum  and  those  of  the  cere- 


*  Meckel's  space  is  formed  by  the  separation  of  the  two  layers  enclosing  the 
Gasserian  ganglion.  The  diaphragma  sellae  is  formed  by  the  dura  proper  attached 
to  the  clinoid  processes  and  having  a  perforation  in  its  centre  for  the  infondibulum 
to  pass  to  the  petuitary  body. 


28  GLANDULE    PACCHIONI. 

bellum  ;  the  third  arches  backwards,  and  supports  the  posterior 
lobes  of  the  cerebrum. 

Falx.  —  This  partition  is  named,  from  its  resemblance  to  the 
blade  of  a  sickle, /^r/,t'.  It  is  received  into  the  longitudinal  fis- 
sure, and  separates  the  two  cerebral  hemispheres.  It  begins 
in  a  point  attached  to  the  crista  galliy  and  gradually  becomes 
broader  as  it  extends  backwards.  Its  upper  edge  is  convex,  and 
attached  to  the  median  groove  on  the  inner  aspect  of  the  vertex 
of  the  skull  ;  its  lower  margin  is  concave  and  free,  and  runs 
along  the  upper  aspect  of  the  callosum.  From  its  base  or 
broadest  part  proceeds  the  sloping  arched  partition  named  ten- 
torijtm.  This  forms  an  arch  for  the  support  of  the  posterior 
lobes  of  the  cerebrum,  so  that  they  may  not  press  upon  the 
cerebellum  beneath.  The  tentorium  is  attached  to  the  trans- 
verse ridge  of  the  occipital  bone,  to  the  superior  border  of  the 
petrous  portion  of  the  temporal  bone,  and  to  the  posterior  and 
anterior  clinoid  processes  of  the  sphenoid.  In  front  there  is 
a  large  oval  opening  to  allow  of  the  passage  of  the  crura. 
The  small  median  partition  which  separates  the  lobes  of  the 
cerebellum  is  called  the  falcida.  It  is  placed  vertically  in  the 
same  plane  with  the  falx,  and  its  point  is  downwards  towards 
the  foramen  magnum.  As  it  approaches  the  foramen  it  usually 
divides  into  two  small  folds. 

Glandulae  Pacchioni.  —  In  the  neighborhood  of  the  supe- 
rior longitudinal  sinus,  we  meet  with  small  white  elevated  gran- 
ulations, sometimes  arranged  singly,  sometimes  in  clusters, 
which  are  received  into  the  depression  on  the  inner  aspect  of 
the  skull-cap.  They  are  termed  glaiidtilce  Pacchioni,  and  are 
found  in  four  situations  :  i.  On  the  outside  of  the  dura,  close 
to  the  superior  longitudinal  sinus,  and  so  large  as  to  occasion 
depressions  in  the  bones.  2.  Along  the  margin  of  the  fissure 
of  Sylvius.  3.  On  the  surface  of  the  pia.  4.  In  the  interior 
of  the  superior  longitudinal  sinus,  covered  by  its  lining  mem- 
brane. 5.  On  the  posterior  and  antero-inferior  parts  of  the 
posterior  lobe  of  the  cerebrum. 


They  are  flue  to  an  increased  growth  of  the  villi,  which  are  nonnally  found  in 
the  arachnoid  membrane,  and  make  their  way,  through  the  dura  or  the  pia,  to  the 
different  situations  in  which  they  are  found.  The  greatest  growth  takes  place 
from  the  visceral  layer,  as  may  be  seen  in  the  dissection  of  the  brain.  These 
bodies  are  not  found  at  birth,  but  usually  commence  their  growth  about  the  third 
year,  and  are  always  found  at  the  seventh  year,  after  which  they  gradually  increase 
as  life  advances. 


SUPERIOR    LONGITUDINAL    SINUS. 


29 


Sinuses  of  the  Dura It  is  one  of  the  peculiarities  of  the 

cerebral  circulation,  that  the  blood  is  returned  through  canals 
or  sinuses  formed  by  the  dura.     These  canals  are  produced  by 
a  splitting  of  the   dura  into  two  layers  as   shown  in  Fig.    5, 
where     i     represents    a    vertical   section 
through  the  superior  longitudinal   sinus. 
They    are    lined    by    the    same    smooth 
membrane   continuous  with   that  of   the 
venous   system.       Since  their  v/alls  con- 
sist  of  unyielding  structure,  and  are  al- 
ways on  the  stretch,   it  is   obvious   that 
they  are  admirably  adapted  to  resist  the 
pressure  of  the  brain.     There  are  fifteen 

of  these  sinuses,  and  they  are  classified  into  two  groups  —  a 
siipero-posterior  and  an  infero  anterior.  The  supero-posterior 
group  comprises  the  superior  longitudinal,  the  inferior  longi- 
tudinal, the  straight,  the  lateral,  and  the  occipital  sinuses  ;  while 
the  infero-anterior  group  includes  the  cavernous,  the  circular,  the 
superior,  and  inferior  petrosal,  and  the  straight  sinuses.  Of  these 
fifteen  sinuses,  five  are  pairs  and  five  are  single,  as  follows  :  — 


Fig.  5.  —  Diagram  to  show 
Formation  of  a  Sinus. 


The  five  pairs  of  sinuses  are  - 
Tiie  lateral. 
The  superior  petrosal. 
The  inferior  petrosal. 
The  cavernous. 
The  occipital. 


The  five  single  sinuses  are  — 

The  superior  longitudinal. 
The  inferior  longitudinal. 
The  circular. 
The  transverse. 
The  straight. 


The  blood  from  all  these  sinuses  is  eventually  discharged  into 

the  internal  jugular  veins. 

Superior  Longitudinal  Sinus.  — This  runs  along  the  upper 

attached  border  of  the  falx  (Fig.  6).      It  begins  very  small  at 

the  foramen  caecum,  gradually 
increases  in  size  in  its  course 
backwards,  and  opposite  the  in- 
ternal protuberance  of  the  oc- 
cipital bone  opens  into  a  tri- 
angular dilatation,  the  torcjclar 
or  the  eojiflnence  of  the  sinuses. 
It  then  divides  into  the  right 
and  left  lateral  sinuses,  the 
right  being  generally  the  larger. 
Besides  numerous  veins  from 
the   cancellous    texture    of    the 

skull-cap,  the  superior  longitudinal  sinus   receives  large  veins 


Fig.  6. 
Superior    longitudinal    sinus.      2.  Inferior 
longitudinal  sinus.     3.  Straight  sinus.     4, 
4.  Venae  Galeni. 


30  DISSECTION. 

from  the  upper  part  of  each  hemisphere  of  the  cerebrum,  and 
an  emissary  vein  through  the  parietal  foramen.  It  is  inter- 
esting to  observe  that  these  veins  run  (as  a  rule)  from  behind 
forward,  contrary  to  the  current  of  blood  in  the  sinus,  and  that 
they  pass  through  the  wall  of  the  sinus  very  obliquely,  like  the 
ureter  into  the  bladder.  The  probable  object  of  this  oblique 
entrance  is  to  prevent  regurgitation  of  blood  from  the  sinus  into 
the  veins  of  the  brain. 

Cut  open  the  superior  longitudinal  sinus  :  observe  that  it  is 
triangular  with  its  base  upwards,  and  that  its  cavity  is  inter- 
sected in  many  places  by  slender  fibrous  cords,  termed  cJiordce 
Willisii.     Their  precise  use  is  not  understood. 

The  brain  should  now  be  removed,  and  preserved  in  alcohol, 
95  proof,  for  future  examination.  Its  anatomy,  with  that  of  its 
remaining  membranes,  will  be  described  in  a  subsequent  part 
of  this  work. 

Dissection The  brain  is  to  be  removed  in  the  following 

manner  :  The  dura  should  be  cut  through  with  a  pair  of  scissors 
on  a  level  corresponding  with  the  sawn  calvaria,  care  being  taken 
to  cut  completely  through  the  falx  in  the  front  part  of  the  longi- 
tudinal fissure.  Now  lift  up  gently,  with  the  fingers  of  the  left 
hand,  the  frontal  lobes  from  the  anterior  fossae,  taking  care  to 
raise  with  the  brain  the  soft  olfactory  lobes  from  the  cribriform 
plate  of  the  ethmoid.  Two  white  flat  nerves  —  the  optic  — 
come  into  view  prior  to  their  leaving  the  skull  through  the  optic 
foramina ;  these  must  be  divided  with  a  sharp  knife  together 
with  the  ophthalmic  arteries  which  lie  beneath  the  correspond- 
ing nerves.  In  the  middle  line,  fixed  firmly  in  the  sella  turcica, 
lies  the  pituitary  body  (hypophisis),  attached  to  the  brain  by  a 
process  —  the  infundibulum.  It  is  not  easy  to  remove  this  body 
from  the  fossa  in  which  it  rests,  owing  to  its  being  retained  in 
its  position  by  dura  {diaphragina  sellae).  When  this  is  removed, 
two  round  white  nerves  —  the  third  —  are  observed,  one  on 
each  side,  lying  on  the  inner  free  border  of  the  tentorium,  im- 
mediately behind  the  anterior  clinoid  process  of  the  sphenoid. 
Divide  these  and  then  proceed  to  cut  through  the  tentorium 
close  to  its  attachment  to  the  posterior  clinoid  process  and  the 
upper  border  of  the  petrous  portion  of  the  temporal  bone,  as  far 
back  as  the  lateral  sinus.  If  this  be  done  with  care,  the  nerves 
lying  beneath  the  tentorium  will  not  have  been  injured.  Imme- 
diately external  to  the  third  nerves  are  the  slender  fourth  nerves  ; 
and  still  further  outside  are  the  soft,  flattened  fifth  nerves.      Cut 


STRAIGHT    SINUS.  31 

these  through,  still  gently  raising  the  brain  from  the  skull  base, 
when  the  seventh  pair  come  into  view  as  they  pass  backwards 
and  outwards  towards  the  internal  auditory  foramina.  When 
these  have  been  cut,  we  notice  the  two  sixth  nerves  running 
directly  forwards  to  pierce  the  dura  covering  the  basilar  process 
of  the  occiput.  Divide  these  as  they  pierce  the  dura,  when  the 
ninth,  tenth,  and  eleventh  nerves  are  brought  well  into  view, 
lying  behind  and  internal  to  the  seventh  and  eighth  ;  the  ante- 
rior one  is  the  glosso-pharyngeal  or  ninth  ;  the  middle  one  is 
the  pneumogastric,  tenth,  and  the  hindermost  one  is  the  spinal 
accessory,  eleventh,  whose  spinal  portion  can  be  traced  coming 
up  from  the  foramen  magnum.  These  all  emerge  through  the 
jugular  foramina.  Below  and  internal  to  these  are  the  hypo- 
glossal or  twelfth,  nerves,  which  usually  pass  through  the  dura 
in  two  fasciculi.  Cut  these,  and  then  pass  down  the  knife  as 
far  into  the  spinal  canal  as  possible,  and  cut  through  the  spinal 
cord,  the  two  vertebral  arteries,  and  the  spinal  portions  of  the 
spinal  accessory  nerves.  Now  lay  the  knife  aside,  when  by 
gentle  traction  the  brain  can  be  easily  removed  from  the  skull. 

The  other  sinuses  should  now  be  examined. 

Lateral  Sinuses.  —  These  are  the  two  great  sinuses  through 
which  all  the  blood  from  the  brain  is  returned  to  the  jugular 
veins.  Their  course  is  well  marked  in  the  dry  skull.  The 
right  is  usually  the  larger.  Each  commences  at  the  internal 
occipital  protuberance,  and  proceeds  at  first  horizontally  out- 
wards, enclosed  between  the  layers  of  the  tentorium,  along  a 
groove  in  the  occipital  bone  and  the  posterior  inferior  angle  of 
the  parietal ;  it  then  descends  along  the  mastoid  portion  of  the 
temporal  bone,  and  again  indenting  the  occipital  bone,  turns 
forwards  to  the  foramen  lacerum  posterius,  and  terminates  in 
the  bulb  of  the  internal  jugular  vein,  where  it  is  joined  by  the 
inferior  petrosal  sinus.  It  receives  blood  also  from  the  inferior 
cerebral  and  cerebellar  veins,  from  the  diploe,  and  the  superior 
petrosal  sinus.  It  communicates  with  the  veins  of  the  scalp 
through  emissary  veins,  which  pass  through  the  mastoid  and 
posterior  condylar  foramina. 

Inferior  Longitudinal  Sinus This   is   of   small   size.       It 

runs  in  the  inferior  free  border  of  the  falx,  and  terminates  in 
the  straight  sinus  at  the  anterior  margin  of  the  tentorium 
(Fig.  6). 

Straight  Sinus. — This  maybe  considered  as  the  continua- 
tion of  the  preceding.      It  runs  along  the  line  of  junction  of  the 


32 


CIRCULAR    SINUS. 


falx  with  the  tentorium,  and  terminates  in  the  torcular  at  the 
divergence  of  the  two  lateral  sinuses.  It  receives  the  inferior 
cerebral  and  the  superior  cerebellar  veins,  and  also  the  two  vencB 
Galeni  (Fig.  6),  which  return  the  blood  from  the  lateral  and 
third  ventricles  of  the  brain. 

Cavernous  Sinus This  is  so  called  because  its  interior  is 

intersected  by  numerous  cords.  It  extends  along  the  side  of 
the  body  of  the  sphenoid  bone,  outside  the  internal  carotid 
artery.     It  receives  the  ophthalmic  vein  which  leaves  the  orbit 


Third  nerve 

Fourth  nerve 

Sixth  nerve 

First  branch  of  the  ) 

fifth  ) 

Superior  petrosal  sinus 
Inferior  petrosal  sinus 


Ophthalmic  vein 

Carotid  artery 
Cavernous  sinus 


Superior 
longitudi 
nal  sinus 


Fig. 


■Diagram  of  the  Venous  Sinuses  at  the  Base  of  the  Skull. 


through  the  sphenoidal  fissure  and  the  anterior  inferior  cerebral 
veins  ;  it  communicates  with  the  circular  sinus  which  surrounds 
the  pituitary  body  or  hypophisis  (Fig.  7).  At  the  apex  of  the 
petrous  portion  of  the  temporal  bone  it  divides  into  the  superior 
and  inferior  petrosal  sinuses. 

Circular  Sinus. — This  surrounds  the  pituitary  body  or 
hypophisis  (p  in  Fig.  7),  and  communicates  on  each  side  with 
the  cavernous  sinus.     The  posterior  branch  is  sometimes  absent. 


MENINGEAL    OK    DUKAL    ARTERIES.  33 

There  may  be  three  channels,  one  in  front,  usually  the  largest, 
another  behind,  and  a  very  small  one  inferiorly,  all  connecting 
the  cavernous  sinuses. 

Petrosal  Sinuses.  —  These  lead  from  the  cavernous  to  the 
lateral  sinuses.  There  are  two  on  each  side.  The  sicperior  runs 
along  the  upper  portion  of  the  pars  petrosa,  in  the  attached 
border  of  the  tentorium  ;  the  inferior,  the  larger  of  the  two,  runs 
along  the  suture  between  the  pars  petrosa  and  the  occipital 
bone,  and  ends  in  the  lateral  sinus  just  before  this  terminates 
in  the  internal  jugular  vein.  The  superior  sinus  receives  the 
inferior  cerebral,  the  superior  cerebellar  veins,  and  a  small  branch 
from  the  tympanum  ;  the  inferior  sinus  is  joined  by  the  inferior 
cerebellar  and  auditory  veins. 

Transverse  Sinus.  — This  extends  from  one  inferior  petrosal 
to  the  other,  across  the  basilar  process  of  the  occipital  bone. 
It  communicates  below  with  the  anterior  spinal  veins. 

Occipital  Sinuses. — These  are  very  small.  They  com- 
mence around  the  margin  of  the  foramen  magnum,  run  in  the 
falcula,  and  uniting  to  form  a  single  sinus,  open  into  the  torcular. 
They  join  inferiorly  with  the  posterior  spinal  veins. 

Meningeal  or  Dural  Arteries.  —  These  arteries  ramify  be- 
tween the  skull  and  the  dura.  Their  course  may  be  traced  by 
the  grooves  which  they  make  in  the  bones.  They  are  termed 
anterior,  middle,  and  posterior,  from  the  fossae  in  which  they 
ramify.* 

The  anterior  nieniiis^cal  are  derived  from  the  ethmoidal  branches  of  the  oph- 
thalmic artery  and  the  cavernous  portions  of  the  internal  carotid.  They  supply 
the  dura  in  the  neighborhood  of  the  ethmoid  bone. 

The  middle  fneningeal  are  three  in  number;  the  most  important  is  the  arteria 
vieiiingea  or  magna  media,  a  branch  of  the  internal  maxillary  artery.  It  enters  the 
skull  through  the  foramen  spinosum,  and  divides  into  two  principal  branches :  one, 
the  anterior,  runs  in  a  groove  near  the  anterior  border  of  the  parietal  bone ;  the 
other,  the  posterior,  curves  backwards  over  the  temporal  bone,  and  subsequently 
ramifies  on  the  parietal  bone.  The  artery  gives  off  a  s.mall  branch  —  \\\& petrosal 
—  which  enters  the  hiatus  Fallopii  and  anastomoses  with  the  stylo  mastoid  arteiy 
in  the  aquxductus  Fallopii ;  one  or  more  anastomosing  branches  which  enter  the 
orbit  through  the  sphenoidal  fissure  to  communicate  with  the  ophthalmic  artery; 
and  some  temporal  branches  which  pierce  the  sphenoid  bone  to  enter  the  temporal 
fossa.  It  is  accompanied  by  two  veins  which  empty  themselves  into  the  internal 
maxillary  vein.  The  arterea  vienengea  parva,  which  enters  the  skull  through  the 
foramen  ovale,  and  a  meningeal  braneh  from  the  ascending  pharyngeal  artery, 
which  comes  up  through  the  foramen  lacerum  medium,  also  supply  the  dura  and 
bones  of  the  middle  fossa. 

The  posterior  meningeal  come  from  the  occipital,  the  ascending  pharyngeal,  and 
the  vertebral  arteries;  the  two  former  enter  the  skull  through  the  foramen  jugu- 
lare,  and  the  latter  through  the  foramen  magnum.  The  meningeal  veins,  witli  the 
exception  of  the  middle  meningeal,  open  into  the  various  sinuses. 

*  A  praedural,  medidural,  postdural,  parvidural. 


34  EXIT    OF    THE    CRANIAL    NERVES. 

The  position  of  the  meningeal  arteries  renders  them  liable  to 
injury  in  fractures  of  the  skull ;  hence  extravasation  of  blood 
between  the  skull  and  dura  is  one  of  the  common  causes  of 
compression  of  the  brain. 

Dissection.  —  The  student  should  now  examine  the  cranial 
nerves  as  they  pass  out  through  the  foramina  in  the  base  of  the 
skull,  and  then  dissect  the  cavernous  sinus. 

Exit  of  the  Cranial  Nerves.  —  The  cranial  nerves  proceed 
in  pairs  through  the  foramina  at  the  base  of  the  skull ;  they  are 
named  first,  second,  third,  fourth,  etc.,  pairs,  according  to  the 
order  of  succession  from  before  backwards.  As  they  pass 
through  the  foramina,  each  receives  a  process  from  the  three 
membranes  of  the  brain,  the  dura,  the  pia,  and  the  arachnoid  ; 
the  two  first  are  gradually  lost  upon  the  nerve,  while  the  arach- 
noid is  reflected  back. 

ThQ  first  is  the  olfactoiy  nerve.  This  cannot  be  seen,  because 
the  olfactory  bulb  has  been  removed  with  the  brain.  From  the 
under  aspect  of  the  bulb  proceed  about  twenty  branches,  which 
pass  through  the  foramina  in  the  cribriform  plate  of  the  ethmoid 
bone,  and  are  arranged  in  two  groups,  — inner  and  outer.  The 
inner  (smaller)  pass  to  the  septum  nasi;  and  the  ojiter  (larger)  to 
the  outer  wall  of  the  nose  as  low  as  the  middle  turbinated  bone. 

The  second  {optic  nerve)  passes  through  the  foramen  opticum 
into  the  orbit  accompanied  by  the  ophthalmic  artery. 

In  order  to  see  the  next  three  pairs  of  nerves,  the  dura  must 
be  carefully  removed  from  the  side  of  the  body  of  the  sphenoid, 
and  the  nerves  traced  as  they  pass  through  the  tentorium. 

The  third  [motor  oculi)  passes  through  the  dura,  close  behind 
the  anterior  clinoid  process,  traverses  the  outer  wall  of  the 
cavernous  sinus,  and  enters  the  orbit  through  the  sphenoidal 
fissure,  where  it  receives  some  filaments  from  the  cavernous 
plexus  of  the  sympathetic. 

Before  passing  through  the  fissure,  it  divides  into  two  branches,  an  upper  and 
a  lower,  which  enter  the  orbit  between  the  two  iieads  of  the  external  rectus. 

The  fourth  (trochlearis),  a  small  nerve,  passes  through  the 
dura  a  little  behind  the  posterior  clinoid  process.  It  passes 
through  the  outer  wall  of  the  cavernous  sinus,  lying  below  the 
preceding  nerve  and  above  the  first  division  of  the  fifth,  and 
then  runs  forwards  through  the  sphenoidal  fiss-^ire.  Here  it  lies 
above  the  third  nerve,  and  is  finally  distributed  to  the  superior 
oblique  muscle,  on  its  orbital  surface. 


EXIT    OF    THE    CRANIAL    NERVES. 


35 


In  passing  through  the  cavernous  sinus  it  receives  some  branches  from  the  sym- 
pathetic plexus.  It  also  communicates  here  with  the  ophthalmic  nerve,  and  sends 
back  a  recurrent  branch  to  supply  the  tentorium  as  far  back  as  the  internal  occipital 
protuberance. 

The  fiftJi  {trifacial)  nerve  passes  through  an  aperture  in  the 
dura  beneath  a  tentorium  attached  to  the  elevated  margins  of 


Olfactory  bulb 


Optic  nerve 


Third  nerve  , 


Fourth  nerve 
Fifth  nerve   . 


Sixth  nerve 


.Seventh  nerve 
Eighth  nerve 

Twelfth  nerve 

Ninth  nerve 
Tenth  nerve 
Eleventh  nerve 


Fig.  8.  —  Diagram  of  the  Exit  of  the  Cranial  Nerves. 

the  concave  surface  on  the  anterior  part  of  the  pars  petrosa 
at  its  apex.  It  consists  of  two  parts  —  a  larger  or  sensory  root, 
and  a  smaller  or  motor.  Upon  its  larger  or  sensory  root  is 
developed  a  large  ganglion,  the  Gasscrian  ganglion;  while  the 
motor  root  lies  below  and  unconnected  with  it.      From  this  gan- 


36  EXIT    OF    THE    CRANIAL    NERVES. 

glion  proceed  the  three  primary  divisions  of  the  nerve  —  the 
ophthalmic,  which  passes  through  the  outer  wall  of  the  cavernous 
sinus  below  the  fourth  nerve,  and  subsequently  enters  the  orbit 
through  the  sphenoidal  fissure. 

While  in  the  cavernous  sinus  this  nerve  receives  filaments  of  communication 
from  the  cavernous  plexus,  and  also  sends  back  a  recurrent  branch  to  supply  the 
tentorium  (Arnold) ;  the  ophthalmic  nerve  is  frequently  intimately  connected  with 
a  branch  of  the  fourth  nerve ;  it  is  also  connected  by  a  small  branch  with  the  sixth 
nerve. 

The  viaxillary,  which  gives  off  a  small  recurrent  branch  to 
the  dura  and  middle  meningeal  artery,  and  then  leaves  the  skull 
through  the  foramen  rotundum  ;  and  the  mandibular,  which 
passes  through  the  foramen  ovale.  The  smaller  or  motor  root 
of  the  fifth  lies  beneath  the  ganglion,  with  which  it  has  no  com- 
munication, and  then  joins  the  mandibular  division  to  supply  the 
muscles  of  mastication  with  motor  power. 

The  sixtJi  {abduceiis)  nerve  pierces  the  dura  behind  the  body 
of  the  sphenoid  bone,  which  it  grooves.  It  then  passes  along 
the  inner  wall  of  the  cavernous  sinus,  external  to  the  internal 
carotid  artery,  and  enters  the  orbit  through  the  sphenoidal  fissure 
to  supply  the  external  rectus,  between  the  two  heads  of  which 
it  passes.  It  is  connected,  as  it  passes  along  the  inner  wall  of 
the  cavernous  sinus,  with  the  cavernous  plexus,  the  ophthalmic 
nerve,  and  in  the  orbit  with  Meckel's  ganglion. 

The  seventh  ox  facial  nei've  passes  through  the  meatus  audi- 
torius  internus,  together  with  the  auditory  nerve  and  artery. 
As  it  passes  along  the  meatus  it  is  separated  from  the  auditory 
nerve,  upon  which  it  lies,  by  the  portio  intermedia  of  Wrisbcrg. 
At  the  bottom  of  the  auditory  meatus,  the  facial  nerve  leaves 
the  auditory  to  traverse  a  tortuous  bony  canal,  the  "aquseductus 
Fallopii."  In  the  meatus  auditorius,  the  facial  and  the  auditory 
nerves  are  connected  by  small  filaments. 

The  eigJitJi  or  auditory  nerve  passes  outwards  through  the 
internal  auditory  meatus  in  company  with  the  preceding  nerve. 
It  is  the  larger  of  the  two  nerves,  and  lies  below  the  facial,  which 
lies  in  a  groove  on  this  nerve.  In  the  meatus  the  auditory 
divides  into  two  branches,  cochlear  and  vestibular. 

The  ninth  or  glosso-phatyngeal  nerve  Y>^?,se?,  through  the  jugu- 
lar foramen  in  front  of  the  pneumogastric  and  spinal  accessory 
nerves.  This  nerve  has  a  separate  tube  of  dura  and  arachnoid, 
and  lies  in  a  groove  in  the  lower  border  of  the  pars  petrosa  of  the 
temporal  bone,  together  with  the  two  succeeding  nerves  (Fig.  9). 


CAVERNOUS    SINUS. 


37 


The  tenth  or  piiciimogastric  nerve  emerges  through  the  jugu- 
lar foramen  behind  and  rather  internal  to  the  glosso-pharyngeal. 
It  is  enclosed  in  a  common  sheath  of  dura  with  the  spinal  ac- 
cessory, but  is  separated  from  it  by  a  thin  septum  of  arachnoid 
membrane. 

The  eleventh  or  spinal  accessory  also  passes  through  the  fora- 
men jugulare,  lying  behind  the  preceding  nerve. 

The  tzuelfth  or  hypoglossal  nerve  passes  through  the  anterior 
condylar  foramen,  piercing  the  dura  by  two  fasciculi  which 
unite  external  to  the  skull. 


INF.PETROSAL 
SINUS 


INT  AUD. MEATUS 


■^(j;?6^GL0SS0-PHARyN6EAl 

PNEU  MO -GASTRIC 

SPINAL  ACCESSORY 
LATERAL  SINUS 


Fig.  g.  — Diagram  showing  the  Relations  of  the  Vessels  and  Nerves  Passing 

THROUGH    THE    FoRAMEN    JUGULARE. 


Dissection.  —  We  must  now  examine  the  cavernous  sinus, 
and  the  nerves  which  course  along  its  walls  to  the  orbit  — 
namely,  the  third,  the  fourth,  the  ophthalmic  division  of  the  fifth 
and  the  sixth  nerves. 

Cavernous  Sinus. — This  sinus  (Fig.  7)  lies  by  the  side  of 
the  body  of  the  sphenoid  bone.  In  front  it  receives  the  ophthal- 
mic vein,  which  passes  backwards  through  the  sphenoidal  fissure  ; 
while  posteriorly  it  divides  into  the  superior  and  inferior  petrosal 
sinuses,  which  have  been  already  described  ;  on  the  inner  side 
it  communicates  with  the  circular  sinus,  which  surrounds  the 
pituitary  body  or  hypophisis  (P  in  Fig.  7).  The  interior  of  the 
sinus  is  remarkable  for  the  numerous  fine  bands  of  reticular 
tissue  which  interlace  in  all  directions. 

In  the  outer  wall  of  the  cavernous  sinus  we  trace,  from  above 
downwards,  the  third  nerve,  the  fourth,  and  the  ophthalmic  di- 


38       RELATIVE    POSITIONS    OF    NERVES    IN    SPHENOIDAL    FISSURE. 

vision  of  tlie  fifth,  in  their  course  to  the  orbit.  On  its  inner  wall 
are  situated  the  internal  carotid  artery  with  the  sixth  nerve 
below  and  to  its  outer  side.     These  structures  are  not  actually 


eAVERNOUS    SINUS 
INT.CAROTID    ARTERV- 


Fig.  10.  — Relation  of  the  Various  Structures  Passing  Through  the 
Cavernous  Sinus. 

within  the  sinus  so  as  to  be  bathed  by  the  blood,  for  they  are 
separated  from  it  by  the  Hning  membrane  of  the  sinus  (Fig.  lo). 
Relative  Positions  of  Nerves  in  Sphenoidal  Fissure. — 
These  nerves  should  be  traced  from  the  cavernous  sinus,  for- 
wards, so  as  to  see  how  they  alter  their  relative  positions  before 
entering  the  sphenoidal  fissure,  and,  again,  in  their  passage 
through  it. 

Just  before  entering  the  sphenoidal  fissure,  the  fourth  nerve 
(on  its  way  to  the  orbital  surface  of  the  superior  oblique)  gets 
above  the  third,  which  here  divides  into  an  upper  and  a  lower 

branch  (both  proceeding  to 
the  ocular  surface  of  the  mus- 
cles they  supply)  ;  lower  still, 
we  have  the  frontal,  lachry- 
mal, and  nasal  divisions  of  the 
ophthalmic ;  lowest  of  all  is 
the  sixth  nerve  on  its  way  to 


LACHRY  MAL 
FRONTAL 


LOWER  DivisioNfioFS"  the  cxtcmal  rectus. 

SIXTH 


In  their  passage  through 
the  sphejioidal  fissnir,  we  find 
that  the  fourth  nerve,  the 
frontal,  and  lachrymal 
branches  of  the  ophthalmic, 
^  lie  at  the  top,  on  nearly  the 

Fig.  11.  — Diagram  of  the  Relations  op  the    same  Icvel,  and  they  CntCr  the 
Nerves   as  thev  pass  through   the   Sphe-  .  .  ,  .^„„„1^o      \^ 

Noii.AL  Fissure.  orbit  above   the   muscles    m 

this  order  from  within  out- 
wards. Lower,  and  in  the  following  order  from  above  down- 
wards, come  the  upper  division  of  the  third,  the  nasal  branch  of 
the  ophthalmic,  the  lower  division  of  the  third,  and  the  sixth  ; 
all  of  which  (with  the  ophthalmic  vein)  enter  the  orbit  between 
the  two  origins  of  the  rectus  cxternus  (Fig.  1 1). 


CURVES  OF  THK  CAROTID  ARTERY. 


39 


At  the  back  of  the  orbit  llie  relation  of  these  nerves  is  further  altered.  The 
fourth,  frontal,  and  lachrymal  are  still  on  the  same  level :  the  upper  division  of  the 
third  is  below  the  sui)erior  rectus,  and  above  the  optic  nerve  is  the  nasal  nerve; 
the  sixth  is  on  the  inner  side  of  the  external  rectus,  while  the  lower  division  of  the 
third  is  below  and  to  the  outer  side  of  the  optic  nerve,  close  to  which  is  the  lentic- 
ular ganglion  [Fig.  12]. 

The  dissector  will  better  remember  the  varying  relations  of  these  nerves  when 
he  has  learnt  their  respective  destinations. 

FRONTAL 


UPPER   DIV.  OFJ      NERVE 
LACHRYMAL 


SIXTH  NERVE 
LI  ARY  GAN  GL. 
LOWER   DIV.OFS""  NERVE 


OPTIC.  N. 

Fig.  12.  —  Relations  of  the  Nerves  and  Muscles  at  the  Back  of  the  Orbit. 


Curves  of  the  Carotid  Artery.  —  After  the  removal  of 
the  cavernous  sinus,  a  good  view  is  obtained  of  the  curves,  hke 
the  letter  S,  made  by  the  inter- 
nal carotid  artery  on  the  side  of 
the  pituitary  fossa.  The  vessel 
enters  the  cranium  at.  the  apex 
of  the  petrous  portion  of  the 
temporal  bone,  makes  its  sig- 
moid curves  within  the  cavern- 
ous sinus,  and  then  passes 
through  the  dura,  between  the 
anterior  clinoid  process  and  the 
optic  nerve,  where  it  gives  off 
the  ophthalmic  artery.  Within 
the  cavernous  sinus,  small 
branches,  ai'tericB  rcceptaculi, 
arise  from  the  carotid  and  sup- 
ply the  pituitary  body  and  the 
walls  of  the  sinus. 


Fig.  13.  — The  Geniculate  Ganglion  of 
THE  Facial  Nerve. 

I.  The  chorda  tympani.  2.  The  geniculate 
ganglion  of  the  facial  nerve.  3.  Ihe  great 
petrosal  nerve.  4.  The  lesser  petrosal 
nerve  lying  over  the  tensor  tympani.  5. 
The  external  petrosal  nerve  communicating 
with  the  sympathetic  plexus  on  the  arteria 
nieningea  media  (6).  7.  The  Gasserian 
ganglion. 


A  careful  dissection  would  show  a  plex- 
us of  sympathetic  nerves  on  the  outer 
side  of  the  internal  carotid  artery,  as  it  lies  by  the  side  of  the  body  of  the  sphenoid. 
This  is  the  carotid  plexis.  It  is  connected  by  numerous  filaments  with  the 
sixth  nerve  and  the  Gasserian  ganglion.  It  further  furnishes  the  large  deep  pe- 
trosal nerve  which  unites  with  the  large  superficial  petrosal  nerve  of  the  facial  to 
form  the  Vidian;  and  also  the  small  deep  petrosal  nerve  which  joins  probably  the 
tympanic  plexus.     Those  filaments  of  the  sympathetic  seen  on  the  inner  side  of  the 


40  DISSECTION    OF    THE    FACE. 

arteiy  in  the  upper  part  of  the  cavernous  sinus  constitute  the  cavernous  plexus, 
which  is  in  communication  -Hith  the  third,  the  fourth,  and  the  ophthalmic  division 
of  the  fifth  nerves,  and  gives  a  branch  to  the  lenticular  ganglion  in  the  orbit. 

On  removing  the  Gasserian  ganglion,  three  small  nerves  are 
seen  lying  on  the  anterior  surface  of  the  petrous  portion  of  the 
temporal  bone.  One,  the  large  superficial  petrosal  nej've,  enters 
the  hiatus  Fallopii  to  join  the  facial ;  the  second,  immediately 
external  to  the  preceding,  is  the  small  superficial  petrosal,  which 
passes  from  the  facial  to  join  the  otic  ganglion  ;  the  third,  the 
external  superficial  petrosal  7ierve  (not  always  present),  passes 
from  the  facial  to  communicate  with  the  sympathetic  on  the 
middle  meningeal  artery. 


DISSECTION    OF    THE    FACE. 

Much  practice  is  required  to  make  a  good  dissection  of  the 
face,  and  it  is  well,  therefore,  to  dissect  this  part  before  the 
skin  and  adjacent  structures  get  dry  and  discolored. 

The  muscles  of  expression  are  numerous  and  complicated  ; 
they  are  interwoven  with  the  subcutaneous  tissue  and  closely 
united  to  the  skin  :  their  fibres  are  often  pale  and  indistinct. 
The  face  is  largely  supplied  with  motor  and  sensory  nerves,  of 
which  the  ramifications  extend  far  and  wide.  Therefore  you  must 
not  be  discouraged  if,  in  a  first  attempt,  you  fail  to  make  a  satis- 
factory display  of  the  parts. 

The  cheeks  and  nostrils  sJiould  be  distejided  with  horse-hair,  a7id 
the  lips  sezan  together. 

Make  an  incision  down  the  mesial  line  of  the  face  ;  another 
from  the  chin  along  the  base  of  the  lower  jaw  to  the  angle  ; 
then  prolong  it,  in  front  of  the  ear,  to  the  zygoma.  Reflect  the 
skin  from  below  upwards.  Each  muscle,  to  be  properly  cleaned, 
should  be  put  on  the  stretch  by  hooks. 

The  student  is  recommended  to  make  out  the  muscles  and 
arteries  on  the  one  side,  leaving  the  other  side  for  the  display  of 
the  nerves. 

The  motor  nerve,  which  supplies  all  the  muscles  of  expression 
in  the  face,  is  the  'portio  dura,'  or  facial  nerve.  It  emerges 
from  the  stylo-mastoid  foramen,  and  divides  into  branches,  which 
pass  through  the  parotid  gland,  forming  a  plexus  termed  the  'pes 
ansc7  inus. ' 

The  sensory  nerves  of  the  face  arc  chiefly  derived  from  the 


OBICULARIS    ORIS.  41 

three  divisions  of  the  fifth  cranial  nerve  ;  namely,  the  supra- 
orbital, the  SLipra-trochlear,  the  lachrymal,  the  infra-trochlear,and 
naso-lobular,  which  latter  supply  the  ala  and  the  tip  of  the  nose  ; 
the  three  sets  of  branches  from  the  infra-orbital  ;  and  the  mental. 
The  other  nerves,  which  confer  sensation  upon  the  face,  are  the 
great  auricular  branch  of  the  cervical  plexus,  which  supplies  the 
skin  covering  the  parotid  gland  and  part  of  the  cheek. 

It  is  convenient  to  arrange  the  muscles  of  the  face  under 
three  groups  ;  appertaining,  respectively,  to  the  mouth,  the  nose, 
the  eyebrows,  and  lids.      Begin  with  those  of  the  mouth. 

The  muscles  of  the  mouth  are  arranged  thus  :  there  is  an 
orbicular  or  sphincter  muscle  surrounding  the  lips  ;  from  this, 
as  from  a  common  centre,  muscles  diverge  and  are  fixed  into 
the  surrounding  bones.  They  are  named  elevators,  depressors, 
sphincters,  etc.,  according  to  their  respective  action. 

Musculus  Risorius  (Santorini). — This  muscle  is  usually 
considered  as  a  part  of  the  platysma  myoides,  the  large  subcuta- 
neous muscle  of  the  neck.  It  arises  by  thin  fasciculi  from  the 
fascia  over  the  masseter  muscle,  and  passes  horizontally  forwards 
to  be  inserted  into  the  angle  of  the  mouth,  where  it  intermingles 
with  the  orbicularis  oris  and  depressor  anguli  oris.  It  produces 
the  smile,  not  of  good-humor,  but  of  derision. 

Obicularis  Oris.  —  This  muscle,  nearly  an  inch  in  breadth, 
surrounds  the  mouth,  forming  a  kind  of  sphincter.  Its  size  and 
thickness  in  different  individuals  produce  the  variety  in  the 
prominence  of  the  lips.  Observe  that  its  fibres,  except  the 
most  internal,  do  not  surround  the  mouth  in  one  unbroken 
series,  but  that  those  of  the  upper  and  lower  lip  decussate  at  the 
angles  of  the  mouth,  and  intermingle  with  the  fibres  of  the 
buccinator  and  other  muscles  which  converge  from  different 
parts  of  the  face. 

The  orbicularis  consists  of  two  parts,  an  inner  or  labial  part, 
and  an  outer  or  facial ;  the  difference  in  appearance  of  the 
fibres  being  very  marked.  The  labial  part  consists  of  pale, 
thin  fibres,  forming  more  or  less  of  the  inner  part  of  the  orbicu- 
laris, and  has  no  attachment  to  bone  ;  the  facial  part  is  thinner 
but  broader,  and  besides  being  connected  with  other  muscles,  is 
attached  to  bone  thus  :  in  the  upper  lip  by  two  fasciculi  on  each 
side,  one  to  the  septum  nasi,  the  other  to  the  alveolar  border 
opposite  the  incisor  teeth  ;  in  the  lower  lip  by  a  single  fascicu- 
lus to  the  mandible  on  each  side  opposite  the  canine  tooth. 
The    cutaneous  surface  of  the  muscle  is  intimately  connected 


42  ■  ZYGOMATICUS    MAJOR    AND    MINOR. 

with  the  lips  and  the  surrounding  skin ;  the  deep  surface  is 
separated  from  the  mucous  membrane  by  the  labial  glands  and 
the  coronary  vessels. 

The  orbicularis  is  the  antagonist  of  all  the  muscles  which 
move  the  lips.  Upon  a  nice  balance  of  their  opposite  actions 
depend  the  play  and  infinitely  varied  expression  of  the  mouth.* 

Depression  Anguli  Oris.  —  This  muscle  arises  broadly  from 
the  oblique  line  of  the  mandible  behind  the  foramen  mentale, 
and  is  inserted  narrowly  into  the  angle  of  the  mouth,  intermin- 
gling with  the  zygomatici,  the  risorius,  and  orbicularis  oris. 
It  is  an  important  muscle  in  the  expression  of  sorrowful  emo- 
tions.    We  see  its  action  when  children  cry. 

Depressor  Labii  Inferioris,  or  Quadratus  Menti.  —  This 
muscle  arises  from  the  oblique  line  of  the  mandible  below  the 
foramen  mentale,  and  is  inserted  into  the  lower  lip,  its  fibres 
intermingling  with  those  of  its  fellow  of  the  opposite  side  and 
the  orbicularis.  It  covers  the  vessels  and  nerves  which  emerge 
from  the  foramen. 

Levator  Menti,  or  Levator  Labii  Inferioris.  —  This 
muscle  arises  from  the  mandible,  from  the  fossa  below  the  in- 
cisor teeth,  and,  passing  down,  is  inserted  into  the  skin  of  the 
chin.  To  see  it,  evert  the  lower  lip  and  remove  the  mucous 
membrane  on  either  side  of  the  fraenum.  There  are  two  of 
them,  one  for  each  side.  Their  action  is  well  seen  when  we 
shave  the  chin,  or  protrude  the  lower  lip. 

Zygomaticus  Major  and  Minor. —  The  zygomaticus  major 
arises  from  the  outer  surface  of  the  malar  bone  close  to  its 
suture  with  the  zygoma,  passes  obliquely  downwards  and  in- 
wards, and  is  inserted  into  the  angle  of  the  mouth,  joining  the 
depressor  anguli  and  orbicularis  oris. 

The  zygomaticus  minor  ai  ises  from  the  outer  surface  of  the 
malar  bone,  in  front  of  the  preceding,  and  is  inserted  into  the 
outer  border  of  the  levator  labii  superioris  near  the  corner  of 
the  mouth.  The  zygomaticus  minor  is  often  absent.  The 
zygomaticus  major  is  the  muscle  of  laughing  :  the  minor 
expresses  sadness. 

Before   examining   the    orbicularis    palpebrarum,   notice    the 

*  In  stronp;  muscular  lips  the  upper  part  of  the  orbicularis  sends  a  small  sub- 
cutaneous slip  of  muscle  from  each  side  alonj,'  the  septum  nasi  nearly  to  the  apex. 
The  interval  between  the  two  slips  corresponds  to  the  furrow  which  leads  from  the 
nose  to  the  lip.  This  is  the  nasolabialis  or  depresso7-  scpti  uariiim  of  Ilaller  and 
Albinus. 


TENDO    OCULI. 


43 


tendo   oculi.     To  make  the  tendon  more  apparent,  the   tarsal 
cartilages  should  be  drawn  outward. 

Tendo  Oculi  or  Palpebrarum.  —  This  tendon  is  a  thin  cord 
about  4  mm.  (i  in.)  in  length,  and  is  readily  felt  at  the  inner  angle 


LKVATOR  niENTI 


Fig.  14. 

of  the  eye  by  drawing  the  eyelids  outwards.  It  is  fixed  to  the 
nasal  process  of  the  maxilla,  in  front  of  the  lachrymal  groove, 
is  U-shaped,  and  passes  horizontally  outwards  ;  one  limb  is  at- 
tached to  the  upper,  the  other  to  the  lower   tarsal   cartilage. 


44 


ORBICULARIS    PALPEP.RARUM. 


The  tendon  crosses  the  lachrymal  sac  a  little  above  the  centre, 
and  furnishes  a  tendinous  expansion  which  covers  the  sac  and 
is  attached  to  the  margin  of  the  bony  groove  which  contains  it. 
To  see  this  expansion  we  must  reflect  that  portion  of  the  orbi- 
cularis palpebrarum  which  covers  the  sac. 

In  puncturing  the  lachrymal  sac  the  knife  is  introduced  below 
the  tendon,  in  a  direction  downwards,  outwards,  and  a  little 
backwards.  We  have  to  divide  the  skin,  a  few  fibres  of  the 
orbicularis,  and  the  fibrous  expansion  from  the  tendo  palpebra- 
rum. The  angular  artery  and  vein  are  situated  on  the  inner 
side  of  the  incision. 

Orbicularis  Palpebrarum. — This  thin,  broad  muscle  sur- 
rounds the  margin  of  the  orbit  and  the  eyelids,  forming  a  sphinc- 
ter.   It  is  attached  on  the  inner  side  to  the  tendo  palpebrarum,  to 


I  a  1 3  5>. 


Fig.  15. — Tendon  of  the  Orbicularis  Palpebrarum,  Showing  the  Union  of  this  Tendon 
WITH  the  Lachkvmal  Sac  and  the  Lachrymal  Canals.     (Sa/>/>ey.) 

I.  Lachrymal  canals.  2,  2.  Commencement  of  these  canals  in  tlie  lids.  3,  3.  Internal  extremity 
of  the  tarsal  cartilages.  4,  4.  Free  border  of  the  lids.  5.  Laclirymal  sac.  6.  Attachment  of 
the  tendo  oculi  to  the  nasal  process  of  the  maxilla.  7.  The  division  of  the  tendo  oculi  into  its 
two  branches.  8,  8.  The  two  branches  ensheathing  the  two  lachrymal  canals  and  attached  to 
the  internal  extremity  of  the  tarsal  cartilages. 

the  nasal  process  of  the  maxilla,  to  the  internal  angular  process 
of  the  frontal  bone,  and  to  the  lower  margin  of  the  orbit. 
From  this  attachment  the  fibres  form  a  series  of  oval  curves, 
taking  a  wide  sweep,  and  pass  uninterruptedly  round  the  eyelids 
and  orbit. 

The  fibres  which  belong  to  the  eyelids  {palpebral portioii)  are 
thin  and  pale,  and  form,  over  each  eyelid,  a  series  of  elliptical 
curves  which  meet  at  the  external  canthus  of  the  lids,  and  are 
loosely  attached  to  the  external  tarsal  ligament.  The  degree  of 
their  curvature  becomes  less  as  they  approach  the  margin  of  the 
lids,  so  that  some  fibres  proceed  close  to  the  lashes. 


THE    EYELIDS.  45 

This  was  first  pointed  out  by  Riolanus,*  and  described  as  the  vtusculus 
ci liar  is  A 

The  fibres  which  spread  over  the  orbital  margins  {orbital por- 
tion) are  thicker  and  redder,  and  mingle,  on  the  forehead,  with 
the  occipito-frontalis  and  corrugator  supercilii,  on  the  cheek, 
with  the  elevators  of  the  upper  lip  and  nose  and  the  zygomati- 
cus  minor. 

No  fat  is  found  on  the  eyelids  ;  nothing  intervenes  between 
the  skin  and  the  muscles  but  loose  connective  tissue,  that  there 
may  be  no  impediment  to  the  free  play  of  the  lids. 

The  orbicular  muscle  not  only  closes  the  eyelids  but  protects 
the  eye.  When  the  eye  is  threatened,  the  muscle  suddenly 
contracts,  presses  the  eye  back  into  the  orbit,  and  contracts  the 
skin  of  the  brow  and  cheek  so  as  to  form  a  soft  cushion  in  front 
of  it.  The  cushion  itself  may  be  severely  bruised,  as  is  seen  in 
a  "black  eye;"  but  the  globe  itself  is  rarely  injured.  When 
the  eye  is  closed,  as  in  winking,  the  palpebral  portion  of  the 
muscle  contracts.  Observe  this  movement,  and  notice  that  the 
lids  are  drawn  slightly  inwards  as  well  as  closed.  The  object 
of  this  inward  motion  is  to  direct  the  tears  towards  the  inner 
angle  of  the  eyelids,  where  they  are  absorbed  by  the  puncta 
lachrymalia. 

The  tensor  tarsi  muscle  is  described  in  the  dissection  of  the 
orbit. 

Since  the  orbicular  muscle  is  supplied  by  the  facial  nerve,  it 
is  affected  in  facial  palsy,  and  the  patient  cannot  close  the  lids. 

Corrugator  Supercilii.  —  This  arises  from  the  inner  end  of 
the  superciliary  ridge  of  the  frontal  bone,  and  is  inserted  into 
the  under  surface  of  the  orbicularis  palpebrarum  and  occipito- 
frontalis.  It  lies  concealed  beneath  these  two  muscles,  and  is 
the  proper  muscle  of  frowning.  Its  nerve  is  derived  from  the 
facial. 

The  present  being  a  good  opportunity  to  examine  the  appen- 
dages {tutaviina  ociili)  of  the  eyes,  postpone  for  the  present  the 
dissection  of  the  remaining  muscles  of  the  face. 

The  Eyelids.  —  The  eyelids  are  two  movable  elliptical  folds 
consisting  of  strata  of  different  tissues.  The  upper  lid  is  large 
and   more   movable   than   the  loxver,  so  that  when  the  eye  is 

*  Anthropologia^  lib.  v.,  cap.  lo. 

t  Strictly  speaking,  the  musculus  ciliaris  arises  from  the  two  little  divisions  of 
the  tendo  oculi,  and  is  inserted  at  the  external  canthus,  into  the  fibrous  tissue 
which  unites  the  two  tarsal  cartilages. 


46  STRUCTURE    OF    THE    EYELIDS. 

closed,  it  is  mainly  by  this  fold.  The  interval  between  the  two 
lids  is  called  the  fissiira  palpebrarum,  which  terminates  on  the 
inner  and  outer  sides  in  two  angles,  the  caiithi.  The  lids  are 
thickest  at  their  borders,  are  somewhat  curved,  and  near  the 
inner  canthus  each  presents  a  slight  elevation,  the  papilla  lacJi- 
lymalis,  at  the  top  of  which  is  a  small  opening,  the  pimctnm 
lachijniale  ;  this  is  the  commencement  of  a  small  canal,  canali- 
culus, which  receives  the  tears  and  conveys  them  to  the  lachry- 
mal sac,  and  thence  through  the  nasal  duct  to  the  nose.  At 
the  inner  canthus  the  two  lids  are  separated  by  an  oval  space, 
the  lacus  lac/uyvialis,  where  the  mucous,  membrane  is  raised 
into  a  rounded  eminence,  the  canincula. 

Caruncula  Lachrymalis.^ — ThQcaruncula  lachrymalis  \s  the 
red  rounded  emhience  situated  at  the  inner  canthus  and  formed 
by  the  conjunctiva.  It  is  composed  of  an  aggregation  of  seba- 
ceous and  sweat  glands  covered  by  mucous  membrane  ;  on  the 
surface  of  it  are  minute  hairs. 

Resting  upon  the  eyeball  external  to  the  caruncle  is  a  slight  vertical  triangular 
fold  of  conjunctiva,  plica  sc7)iihinar2S,  which  is  the  rudimentai7  membraiia 
nictitans  (the  third  eyelid  found  in  birds).  Both  in  the  caruncle  and  plica  semilu- 
naris unstriped  muscular  tissue  has  been  demonstrated. 

The  conjunctiva  is  the  mucous  membrane  which  covers  the 
inner  surface  of  the  lids  and  the  front  of  the  eyeball.  The  por- 
tion lining  the  lids  is  termed  tht  palpebral ;  that  portion  cover- 
ing the  front  of  the  eye,  the  ocular.  The  angle  of  its  reflection 
from  the  lids  to  eyeball  is  called  the  foiiiix  conjunctives,  where 
are  situated  a  number  of  racemose  glands  ;  there  is  also  some 
lymphoid  tissue  found  in  other  parts  of  the  conjunctiva.  The 
palpebral  conjunctiva  is  more  vascular  than  the  ocular,  and  it 
presents  a  number  of  minute  papillae,  which,  when  enlarged  and 
aggregated  by  inflammation,  give  rise  to  the  disease  called 
"granular  lids."  The  conjunctiva  will  be  more  fully  described 
with  the  anatomy  of  the  eye. 

The  eyelashes  (cilia)  are  placed  in  two  or  more  rows  along 
the  edges  of  the  tarsal  cartilages.  The  eyelashes  of  the  upper 
lid  are  longer  and  more  numerous  than  in  the  lower ;  and  their 
convexity  is  directed  downwards,  while  those  of  the  lower  lid 
present  an  opposite  curve.  The  bulbs  of  the  lashes  are  situ- 
ated between  the  tarsal  cartilage  and  the  fibres  of  the  orbi- 
cularis palpebrarum.  They  are  supplied  with  blood  by  the 
palpebral  branches  of  the  ophthalmic  artery,  which  run  parallel 
and  close  to  the  free  borders  of  the  lids  beneath  the  orbicular 
muscle. 


TARSAL    CARTILAGES    AND    LIGAMENTS.  47 

Structure  of  the  Eyelids. — The  eyelids  are  composed  of 
different  tissues,  arranged  in  successive  strata  one  beneath  the 
other.  They  are — i.  The  skin;  2.  The  orbicuiatis  palpe- 
brarimi ;  3.  The  palpebral  ligament,  which  extends  from  the 
margin  of  the  orbit  to  the  cartilage  ;  4.  The  expanded  tendon  of 
the  levator palpebrce  (in  the  upper  Hd  only)  ;  5.  The  tarsal  carti- 
lage ;  6.  A  thin  layer  of  fascia,  in  which  are  seen  the  blood- 
vessels ;  7.  The  Meibomian  glands,  which  lie  embedded  in  the 
tarsal  cartilage  ;  8.  Conjunctiva.  These  structures  are  severally 
connected  by  areolar  tissue,  which  never  contains  fat. 

Such,  in  outline,  is  the  structure  of  the  eyelids.  Their  use  is 
best  described  by  Socrates,  who,  in  answer  to  the  question 
whether  animals  were  made  by  chance  or  design,  replies : 
"  Think  you  not  that  it  looks  like  the  work  of  forethought,  be- 
cause the  sight  is  delicate,  to  guard  it  with  eyelids  as  with  shut- 
ters, which  open  when  we  want  to  see,  and  shut  during  sleep ; 
and,  that  even  winds  may  not  hurt  them,  to  make  eyelashes  in 
the  lids  for  a  sieve ;  and  to  furnish  the  parts  over  the  eyes  with 
eyebrows,  as  with  eaves,  so  that  even  the  sweat-  from  off  the 
head  may  do  them  no  mischief .''  "  * 

The  skiji  of  the  eyelids  is  remarkably  smooth  and  delicate, 
and  destitute  of  fat.  It  is  abundantly  supplied  with  sensory 
nerves  by  branches  of  the  fifth  pair  —  namely,  by  the  supra- 
orbital, supra-trochlear,  infra-trochlear,  lachrymal,  and  infra- 
orbital nerves. 

The  orbicularis palpcbraruni  has  been  aheady  described  (p.  44).  It  is  supplied 
by  the  facial  nerve. 

The  levator  palpebral  arises  from  the  lesser  wing  of  the  sphe- 
noid above  the  optic  foramen,  gradually  becomes  broader,  and 
terminates  in  a  thin  aponeurosis,  which  unites  with  the  broad 
tarsal  ligament,  and  is  lost  on  the  upper  surface  of  the  superior 
tarsal  cartilage. 

Tarsal  Cartilages  and  Ligaments. — These  are  plates  of 
dense  connective  tissue,  which  support  and  give  shape  to  the 
eyelids.  There  is  one  for  each  lid,  and  they  are  connected  at  the 
angles  (commissures  or  canthi)  of  the  lids  through  the  medium  of 
fibrous  tissue.  They  can  best  be  examined  by  everting  the  lids. 
Each  cartilage  resembles  its  lid  in  form.  The  upper  is  the  larger, 
is  broad  in  the  middle,  and  gradually  becomes  narrower  at  either 
end.     The  lower  is  nearly  of  uniform  breadth  throughout.     Both 

*  Xenophon's  Memorabilia,  b.  i,  c.  vi.,  §  6. 


48 


PUNCTA    LACHRYMALIA. 


are  thicker  on  the  nasal  than  on  the  temporal  side.  They  are 
connected  to  the  margin  of  the  orbit,  and  maintained  in  position 
by  the  broad  tarsal  ox  palpebral  ligament ;  this  is  a  continuation 
from  the  periosteum  of  the  orbit  to  the  tarsal  cartilage,  and  is 
denser  at  the  outer  part  of  the  orbit.  There  are  two  of  them  — 
upper  and  lower  —  and  they  pass  to  each  cartilage  respectively. 
When  an  abscess  forms  in  the  connective  tissue  of  the  lids, 
these  ligaments  prevent  the  matter  from  making  its  way  into 
the  orbit. 


Fig    i6  — Muscles  of  the  Eye      Ligament  of  Zinn. 

I.  Attachment  of  the  ligament  of  Zinn  — showing  the  three  tongue-Hke  projections,  from  its  annu- 
lar parts  surrounding  the  optic  nerve,  to  the  internal,  external,  and  inferior  recti  muscles. 
2.  External  rectus,  incised  and  deflected  downwards  to  show  the  internal  rectus.  3.  Internal 
rectus.  4.  Inferior  rectus.  5.  Superior  rectus.  6.  Superior  oblique.  7.  Pulley  for  the  supe- 
rior oblique  muscle.  8.  Inferior  oblique.  9.  Levator  palpebrae.  10.  Portion  of  the  orbicu- 
laris palpebrarum.     II.  Optic  nerve. 

Each  tarsal  cartilage  is  attached  on  its  outer  side  to  the  malar 
bone  by  the  external  tarsal  ligament,  and  on  its  side  to  the  nasal 
process  of  the  maxilla  by  the  tendo  palpebrarum  or  the  internal 
tarsal  ligament. 

The  free  or  ciliary  margin  is  straight,  and  is  the  thickest  part  of  the  tarsal  car- 
tilages. It  is  generally  .stated  that  the  inner  edge  of  each  is  sloped  or  bevelled 
off;  and  that,  when  the  lids  are  closed,  there  is  formed,  ivith  the  globe  of  the  eye. 
a  triangular  channel.  This  channel  is  said  to  conduct  the  tears  to  the  puncta 
lachrymalia.  According  to  our  observation,  this  channel  does  not  exist ;  for  when 
the  lids  are  closed,  their  margins  are  in  such  accurate  apposition,  that  not  the 
slightest  interspace  can  be  discovered  between  them. 

Puncta  Lachrymalia. — i:\\<i  puncta  lachrymalia  are  two 
pin-hole  apertures,  easily  discovered  on  the  margin  of  the  lids, 
close  to  the  inner  angle.     They  are  the  orifices  of  the  canals, 


TENSOR    TARSI.  49 

called  canalicidi,  which  pass  inwards  and  convey  the  tears  into 
the  lachrymal  sac. 

Observe  that  their  orifices  are  directed  backwards.  The  upper  canahculus,  the 
longer  and  narrower  of  the  two,  ascends  for  a  short  distance  nearly  vertically,  and 
then  dilating  into  a  small  pouch  makes  a  sharp  bend  inwards  for  about  a  quarter  of 
an  inch  to  join  the  lachrymal  sac ;  the  lower  canal  descends  perpendicularly,  and, 
like  the  upper,  makes  a  sharp  bend,  after  which  it  pursues  a  direction  upwards  and 
inwards  to  the  sac. 

The  two  canals  open  separately 
into  the  sac  (sometimes  by  a  com- 
mon orifice).  In  facial  palsy,  the 
tensor  tarsi  being  affected,  the 
puncta  lose  their  proper  direction, 
and  the  tears  flow  over  the  cheek. 

In  the  introduction  of  probes  for 
the  purpose  of  opening  the  con- 
tracted puncta,  or  of  slitting  up 
the  lachrymal  ducts,  it  is  neces- 
sary to  know  the  exact  direction  of  these  canals.  (Fig. 
17.)  When  from  any  cause  the  tears  are  secreted  in  greater 
quantity  than  usual,  they  overflow  and  trickle  down  the  cheek. 

Meibomian  Glands.  —  These  long  compound  sebaceous  glands,  so  called  after 
the  anatomist  *  who  first  described  them,  are  situated  on  the  under  surface  of  each 
of  the  tarsal  cartilages.  In  the  upper  lid  there  are  between  twenty  and  thirty ;  not 
quite  so  many  in  the  lower.  On  everting  the  lid,  they  are  seen  running  in  longi- 
tudinal parallel  rows  in  grooves  in  the  cartilage.  Under  the  microscope,  each  is 
seen  to  consist  of  a  straight  central  tube,  round  the  sides  of  which  are  a  number  of 
openings  leading  to  short  caecal  dilatations.  The  orifices  of  these  glands  are  situ- 
ated on  the  free  margin  of  the  lids  behind  the  lashes.  They  are  fined  with  flat- 
tened epithelial  cells  which,  in  the  Cciecal  dilatations  and  ducts,  become  cubical  and 
filled  with  fat.  Their  function  is  to  secret  a  sebaceous  material,  which  prevents 
the  lids  from  sticking  together. 

Tensor  Tarsi.  —  This  muscle  is  only  a  deeper  part  of  the 
orbicularis  palpebrarum,  and  lies  just  behind  the  tendo  palpebra- 
rum. To  expose  it,  cut  perpendicularly  through  the  middle  of 
the  upper  and  lower  lids,  and  turn  the  inner  halves  towards  the 
nose.  After  removing  the  mucous  membrane,  the  muscle  will 
be  seen  arising  from  the  ridge  of  the  lachrymal  bone.  It  passes 
nearly  horizontally  outwards  for  about  6.5  mm.,  or  \  inch,  and 
then  divides  into  two  portions,  which  are  inserted  into  the  upper 
and  lower  tarsal  cartilages,  close  to  the  orifices  of  the  lachrymal 
ducts.  It  is  probable  that  the  tensor  tarsi  draws  backwards 
the  open   mouths  of  the  ducts,   so  that  they  may  receive  the 

*  H.  Meibom. 


50 


COMPRESSOR    NARIS. 


tears  at  the  inner  angle  of  the  eye.  It  is  supplied  by  a  small 
branch  from  the  facial  nerve. 

Let  us  now  examine  the  muscles  in  connection  with  the  nose : 
namely  —  the  pyramidalis  nasi,  the  compressor  naris,  the  de- 
pressor alas  nasi,  and  the  smaller  intrinsic  muscles  of  the  nose. 
All  are  supplied  by  the  facial  nerve. 

Pyramidalis  Nasi. —  This  is  situated  on  the  bridge  of  the 
nose,  one  on  each  side  of  the  mesial  line,  and  is  usually  regarded 
as  a  continuation  of  the  inner  part  of  the  occipito  frontalis.  The 
two  muscles  diverge  as  they  descend,  and  their  fibres  blend  with 


^^3"—  8.sAMa> 

Fig.  i8.  —  Tensor  Tarsi-Attachment  of  the   Orbicui.akis   Palpebrarum  to  the  Inner 
Part  of  the  Base  of  the  Orbit.     {Sappey.) 

1,  1.  Inner  wall  of  the  orbit.  2,  2.  Internal  part  of  the  orbicularis  palpebrarum.  3,  3.  Attachment 
of  this  muscle  to  the  circumference  of  the  base  of  the  orbit.  4.  Opening  for  the  nasal  artery. 
5.  Tensor  Tarsi.  6,6.  Posterior  view  of  the  lids.  7,7.  Orbital  portion  of  the  lachrymal  gland. 
8,  9,  10.  Palpebral  portion  of  this  gland.     11,  11.  Mouths  of  its  excretory  ducts. 

those  of  the  compressor  naris.  Their  action  produces  transverse 
wrinkles  of  the  skin  at  the  root  of  the  nose,  as  in  the  expression 
of  an  aggressive  feeling. 

Compressor  Naris.  —  This  muscle  is  triangular,  and  arises 
by  its  apex  from  the  inner  side  of  the  canine  fossa  of  the  maxilla, 
and  is  attached  to  a  broad  thin  aponeurosis  which  spreads  over 
the  dorsum  of  the  nose,  and  joins  its  fellow.  The  origin  of  this 
muscle  is  concealed  by  the  levator  labii  superioris  ala^que  nasi. 

When  this  muscle  is  reflected  from  its  junction  with  its  fel- 
low, a  small  nerve  is  seen  running  down  towards  the  tip  of  the 
nose.     This  nerve  is  the  superficial  branch  oi  the  nasal  nerve 


COMPRESSOR    NARIS. 


51 


(called  also  naso-lobnlai).  It  becomes  subcutaneous  between 
the  nasal  bone  and  the  cartilage,  and  supplies  the  tip  and  lobule 
of  the  nose.  It  is  joined  by  a  branch  of  the  facial  nerve  at  its 
termination. 


Fig.  ig. 


Depressor  Alae  Nasi.  —  This  arises  from  the  maxilla,  above  the  second  incisor 
tooth,  and  is  inserted  into  the  septum  and  ala  of  the  nose.  It  is  situated  between 
the  mucous  membrane  and  the  muscular  structure  of  the  upper  lip;  so  that,  to 
expose  it,  the  upper  lip  must  be  everted,  and  the  mucous  membrane  removed. 

Besides  the  muscles  above  described,  we  find  in  connection  with  the  cartilages 


52  BUCCINATOR, 

of  the  alas  of  the  nose,  pale  muscular  fibres  which  have  no  very  definite  arrange- 
ment and  require  a  lens  for  their  detection.  The  dilatator  jiaris posterior  arises 
from  the  nasal  process  of  the  maxilla  and  the  sesamoid  cartilages,  and  is  inserted 
into  the  skin  of  the  margin  of  the  nostril ;  the  dilatator  naris  anterior  descends 
vertically  from  the  cartilage  of  the  aperture  to  its  free  margin.  The  action  of 
these  small  muscles  is  to  raise  and  evert  the  ala  of  the  nose,  and  to  counteract 
its  tendency  to  be  closed  by  atmospheric  pressure.  In  dyspnoea,  and  in  certain 
mental  emotions,  they  contract  with  great  energy. 

Levator  Labii  Superioris  Alaeque  Nasi,  or  Levator  Labii 
Superioris  et  Alae  Nasi.  —  This  ^m^'j- from  the  nasal  process 
of  the  maxilla  near  its  orbital  margin,  and  passing  downwards 
divides  into  two  portions  :  an  inner  inserted  into  the  side  of  the 
ala  of  the  nose  ;  an  outer,  into  the  upper  lip,  where  its  fibres 
blend  with  the  orbicularis  oris  and  levator  labii  superioris.  It 
acts  chiefly  in  expressing  the  smile  of  derision.  Its  habitual 
use  occasions  the  deep  furrow  which,  in  most  faces,  runs  from 
the  ala  of  the  nose  towards  the  corner  of  the  mouth. 

Levator  Labii  Superioris  Proprius.  —  This  arises  from  the 
lower  margin  of  the  orbit,  i.e.,  from  the  maxilla  and  malar  bones, 
above  the  infra-orbital  foramen,  and  is  ijiserted  into  the  upper 
lip,  where  its  fibres  blend  with  the  orbicularis  oris.  It  is  nearly 
an  inch  in  breadth  at  its  origin,  which  covers  the  infra-orbital 
vessels  and  nerves,  and  is  itself  overlapped  by  the  orbicularis 
palpebrarum. 

Levator  Anguli  Oris.  —  This  muscle,  which  is  covered  by 
the  levator  labii  superioris,  arises  from  the  canine  fossa  of  the 
maxilla,  below  the  infra-orbital  foramen,  and  is  inserted  into  the 
angle  of  the  mouth,  superficial  to  the  buccinator,  its  fibres 
blending  with  those  of  the  orbicularis  oris,  the  zygomatic!,  and 
the  depressor  anguli  oris. 

Buccinator,  —  The  buccinator  arises  from  the  outer  surface 
of  the  alveolar  borders  of  the  maxilla  and  mandible  correspond- 
ing to  the  molar  teeth,  and  behind  from  the  pterygo-mandibular 
ligament.  The  fibres  pass  forwards  and  converge,  to  be  inserted 
into  the  angle  of  the  mouth  and  the  muscular  structure  of  the 
lips  ;  the  central  fibres  decussate,  while  the  upper  fibres  pass  to 
the  upper  lip,  and  the  lower  fibres  pass  to  the  lower  lip.  The 
muscle  is  covered  on  its  inner  aspect  by  the  mucous  membrane 
of  the  cheek,  and  on  its  outer  by  a  thin  fascia  which  passes 
backwards,  and  is  continuous  with  that  covering  the  pharynx. 

The  buccinator  is  the  principal  muscle  of  the  check.  It  forms 
with  the  superior  constrictor  of  the  pharynx  a  continuous  muscu- 
lar wall  for  the  side  of  the  mouth  and  pharynx.     The  bond  of 


BUCCINATOR. 


53 


connection  between  the  buccinator  and  the  superior  constrictor 
is  a  tendinous  band,  the  ptcrygo-niandibulay  ligamejit.  This 
li"-ament  (Fig.  20)  extends  from  the  hamular  process  vertically 
to  the  posterior  extremity  of  the  mylo-hyoid  ridge  of  the  man- 
dible near  the  last  molar  tooth.  It  is  simply  a  fibrous  intersec- 
tion between  the  two  muscles. 


Obicularis  oris 

Pterygo-mandibular  ( 
ligament. 


Mylo-hyoidens 

Os  hyoide 

Thyro-hyoid  ligament 

Pomum  Adam 


Cricoid  cartilage 
Trachei 


pharyngeal  n. 
pliaryngeus. 


Superior  laryngeal 
n.  and  a. 


External  laryngeal  n. 
Crico-tliyroideus. 

Inferior  laryngeal  n. 
Oesophagus. 


Fig.  20.—  Muscles  of  the  Pharynx. 


The  duct  of  the  parotid  gland  pierces  the  buccinator  obliquely, 
and  opens  into  the  mouth  opposite  the  second  molar  tooth  of  the 
maxilla. 

The  chief  use  of  the  buccinator  is  to  keep  the  food  between 
the  teeth  during  mastication.  It  can  also  widen  the  mouth.  Its 
power  of  expelling  air  from  the  mouth,  as  in  whistling  or  playing 


54    .  FACIAL    ARTERY, 

on  a  wind  instrument,  has  given  rise  to  its  peculiar  name.  It 
is  supplied  by  the  facial  nerve,  and  is,  therefore,  affected  in 
facial  paralysis. 

The  buccinator  is  in  relation,  externally  and  behind,  with  a 
large  amount  of  buccal  fat,  with  the  masseter  and  temporal 
muscles ;  in  front  with  the  risorius,  the  levator  anguli  oris, 
depressor  anguli  oris,  the  zygomatici,  the  duct  of  the  parotid 
gland,  the  facial  artery  and  vein,  and  the  facial  and  buccal 
nerves  ;  internally  with  the  mucous  membrane  of  the  mouth 
and  buccal  glands  ;  and  posteriorly  with  the  pterygo-mandibular 
ligament. 

Buccal  Fascia.  —  The  buccinator  muscle  is  covered  by  a  thin  layer  of  fascia 
which  adheres  closely  to  its  surface,  and  is  attached  to  the  alveolar  border  of  the 
maxilla  and  mandible.  This  structure  is  thin  over  the  anterior  part  of  the  muscle, 
but  more  dense  behind,  where  it  is  continuous  with  the  aponeurosis  of  the  pharynx. 
It  is  called  the  biicco-pharyngeal  fascia,  since  it  supports  and  strengthens  the  mus- 
cular walls  of  these  cavities.  In  consequence  of  the  density  of  this  fascia,  ab- 
scesses do  not  readily  burst  into  the  mouth  of  the  pharynx. 

Buccal  and  Molar  Glands.  —  The  buccal  glands,  in  structure  compound  race- 
mose like  the  salivary,  are  situated  between  the  buccinator  and  the  mucous  mem- 
brane. They  resemble  the  labial  glands  found  beneath  the  mucous  membrane  of 
the  lips,  though  somewhat  smaller.  Three  or  four  other  glands,  about  the  size 
of  a  little  split  pea,  .should  be  made  out,  as  they  lie  between  the  masseter  and  buc-' 
cinator;  these  are  the  molar  glands.  Their  secretion,  said  to  be  mucous,  is  con- 
veyed to  the  mouth  by  separate  ducts  near  the  last  molar  teeth. 

Between  the  buccinator  and  the  masseter,  there  is,  in  almost 
all  subjects,  an  accumulation  of  fat.  It  is  found,  beneath  the 
zygoma  especially,  in  large  round  masses,  and  may  be  turned 
out  with  the  handle  of  the  scalpel.  It  helps  to  fill  up  the  zygo- 
matic fossa,  and  being  soft  and  elastic,  presents  no  obstacle  to 
the  free  movements  of  the  mandible.  Its  absorption  in  ema- 
ciated individuals  occasions  the  sinking  of  the  cheek. 

Facial  Artery.  —  The  facial  (external  maxillary)  artery  is 
the  third  branch  of  the  external  carotid.  It  ascends  tortuously 
beneath  the  posterior  belly  of  the  diagastricus  and  the  stylo- 
hyoideus,  next  through  or  under  the  substance  of  the  subman- 
dibular gland  ;  it  then  rests  upon  the  mylo-hyoideus,  and 
subsequently  mounts  over  the  base  of  the  mandible  at  the  ante- 
rior  edge  of  the  vtasseter  muscle.  This  part  of  the  course  of 
the  facial  will  be  fully  examined  further  on  in  the  dissection  of 
the  neck.  It  now  ascends  tortuously  near  the  corner  of  the 
mouth  and  the  ala  of  the  nose,  towards  the  inner  angle  of  the 
eye,  where,  much  diminished  in  size,  it  inosculates  with  the  ter- 
minal branch  of  the  ophthalmic,  a  branch  of  the  internal  carotid. 


FACIAL    ARTERY. 


55 


In  the  first  part  of  its  course  on  the  face,  the  artery  is  covered 
by  the  platysma  and  the  deep  fascia ;  above  the  corner  of  the 
mouth  it  is  crossed  by  a  few  fibres  of  the  risorius  and  the  zygo- 
matic! ;  still  higher  it  is  covered  by  some  of  the  fibres  of  the 
elevator  of  the  upper  lip.*  It  lies  successively  upon  the  bucci- 
nator, levator  anguli  oris,  and  levator  labii  superioris  alaique  nasi 


Fig.  21.  —  Branches  of  the  External  Carotid  Artery. 

I.  External  carotid.  2  Lingual.  3.  Facial.  4.  Inferior  labial.  5.  Inferior  coronary.  6.  Supe- 
rior coronary.  7.  Lateral  nasal.  8.  Angular,  q.  Superior  thyroid,  10  and  16.  Occipital. 
II.  Posterior  auricular.  12.  Anterior  auricular.  13.  Internal  maxillary.  14.  Transverse  facial. 
15.  Middle  temporal.  17.  Anterior  temporal.  18.  Posterior  temporal.  19.  Supraorbital. 
20.   Frontal. 

muscles.      In  its  course  along  the  face  it  gives  off  the  following 
branches  :  — 

a.  The  inferior  labial  artery  passes  inwards  under  the  depressor  anguli  oris 
and  inosculates  with  the  mental  branch  of  the  inferior  dental,  the  inferior  coronary, 
and  the  submental  arteries. 

*  Not  infrequently  the  artery  lies  superficial  to  this  muscle. 


56  THE    FACIAL    VEIN. 

l>.  The  inferior  coronary  arteiy  comes  off  near  the  angle  of  the  mouth,  either 
directly  from  the  facial,  or  in  common  with  the  superior  coronary.  It  runs  tortu- 
ously along  the  lower  lip,  beneath  the  depressor  anguli  oris ;  it  then  pierces  the 
orbicularis,  running  between  this  muscle  and  the  mucous  membrane  of  the  lip.  It 
inosculates  largely  with  its  fellow,  the  inferior  labial  and  the  mental  arteries. 

c.  The  superior  coronary,  larger  than  the  preceding,  is  given  off  beneath  the 
zygomatici.  It  proceeds  along  the  upper  lip  close  to  the  mucous  membrane,  and 
inosculates  with  its  fellow;  thus  is  formed  round  the  mouth  a  complete  arterial 
circle,  which  can  be  felt  pulsating  on  the  inner  side  of  the  lip,  near  the  free  bor- 
der. From  this  circle  numerous  branches  pass  off  to  the  papilla;  of  the  lips  and 
the  labial  glands.  The  superior  coronary  gives  off  a  branch,  t/w  artery  of  the  sep- 
tum, which  ascends  along  the  septum  to  the  apex  of  the  nose ;  also  a  small  one  to 
the  ala  nasi. 

d.  The  lateral  artery  of  the  nose,  a  branch  of  considerable  size,  arises  oppo- 
site the  ala  nasi,  ramifies  upon  the  external  surface  of  the  nose,  and  "inosculates 
with  the  nasal  branch  of  the  ophthalmic  artei"y,  the  infra  orbital,  and  the  artery  of 
the  septum. 

e.  The  angular  artery,  which  may  be  regarded  as  the  termination  of  the 
facial,  inosculates  on  the  inner  side  of  the  tendo-palpebrarum  with  the  nasal  branch 
of  the  ophthalmic  artery. 

The  facial  artery  supplies  numerous  branches  to  the  muscles 
of  the  face,  and  inosculates  with  the  transversalis  faciei,  infra- 
orbital, the  mental,  the  sublingual  branch  of  the  lingual,  the 
nasal  branches  of  the  internal  maxillary  and  the  ophthalmic,  the 
ascending  pharyngeal  and  descending  palatine  arteries. 

The  facial  artery  and  its  branches  are  surrounded  by  a  minute 
plexus  of  nerves  (nervi  molles)  invisible  to  the  naked  eye.  They 
are  derived  from  the  superior  cervical  ganglion  of  the  sympa- 
thetic, and  exert  a  powerful  influence  over  the  contraction  and 
dilatation  of  the  capillary  vessels,  and  thus  occasion  those  sudden 
changes  in  the  countenance  indicative  of  certain  mental  emotions, 
e.g.,  blushing  or  sudden  paleness. 

The  facial  vein  does  not  run  with  the  artery,  but  takes  a 
straight  course  from  the  inner  angle  of  the  eye  to  the  anterior 
border  of  the  masseter.  In  this  course  it  descends  upon  the 
levator  labii  superioris,  then  passes  beneath  the  zygomatic  mus- 
cles, over  the  termination  of  the  parotid  duct,  and  at'the  anterior 
border  of  the  masseter  passes  over  the  mandible,  behind  the 
facial  artery,  and  joins  the  internal  jugular. 

The  facial  vein  is  a  continuation  of  the  frontal,  which  descends  over  the  fore- 
head, and,  after  receiving  the  supra.orbital,  takes  the  name  of  aui^ular  at  the  cor- 
ner of  the  eye.  It  communicates  with  the  ophtlialmic  vein,  receives  the  veins  of 
the  eyelid.s,  the  external  part  of  the  nose,  the  coronary  veins,  and  others  from  the 
muscles  of  the  face.  Near  the  angle  of  the  mouth  it  is  increased  in  size  by  a  com- 
municating branch  from  the  infraorbital  vein,  and  by  a  large  vein  which  comes 
from  the  temporomandibular  vein.  The  other  veins  which  empty  themselves  into 
the  facial  correspond  with  the  branches  given  off  from  the  facial  artery. 


PAROTID    GLAND.  57 

Arteria  transversalis  faciei. — This  artery  arises  from  the 
temporal,  or  occasionally  from  the  external  carotid  in  the  sub- 
stance of  the  parotid  gland.  It  runs  forwards  across  the  masse- 
ter  between  the  parotid  duct  and  the  zygoma,  and  is  distributed 
to  the  glandula  socia  parotidis,  and  the  masseter.  It  anastomoses 
with  the  infra-orbital,  buccal,  and  facial.  It  is  seldom  of  large 
size,  except  when  it  supplies  those  parts  which  usually  receive 
blood  from  the  facial.  We  have  seen  it  as  large  as  a  goose-quill, 
furnishing  the  coronary  and  the  nasal  arteries,  the  facial  itself 
not  being  larger  than  a  sewing-thread. 

The  parotid  gland  is  now  to  be  examined.  Its  boundaries,  its 
deep  relations,  the  course  of  its  duct,  and  the  objects  contained 
within  the  gland,  must  be  carefully  observed. 

Parotid  Gland. — The  parotid,  the  largest  of  the  salivary 
glands,  occupies  the  space  between  the  ramus  of  the  mandible 
and  the  mastoid  process,  and  weighs  between  five  and  eight 
drachms  (20  to  32  gm.).  It  is  bounded  above  by  the  zygoma  ; 
below,  by  the  sterno-mastoid  and  digastric  muscles  ;  behind,  by 
the  meatus  auditorius  externus  and  the  mastoid  process ;  in 
front,  it  lies  over  the  ascending  ramus  of  the  mandible,  and  is 
prolonged  for  some  distance  over  the  masseter.  Internally  it  is 
in  contact  with  the  styloid  process,  and  the  sheath  of  the  internal 
carotid  and  jugular  vein.  It  is  separated  from  the  subman- 
dibular gland  by  the  stylo-mandibular  ligament ;  sometimes  the 
two  glands  are  directly  contiguous. 

The  superficial  surface  of  the  gland  is  flat,  and  covered  by  a 
strong  layer  of  fascia,  a  continuation  of  the  cervical,  and  has  one 
or  two  lymphatic  glands  lying  on  it. 

It  not  only  surrounds  the  gland,  but  sends  down  numerous  partitions  which 
form  a  framework  for  its  lobes.  The  density  of  this  sheath  explains  the  pain 
caused  by  inflammation  of  the  gland,  the  tardiness  with  which  abscesses  within  it 
make  their  way  to  the  surface,  and  the  propriety  of  an  early  opening.  [The  only 
open  space  in  its  capsule  being  at  the  styloid  process,  an  abscess  may  ascend  into 
the  temporal  fossa  or  go  into  the  retropharyngeal  region.  — A.  H.] 

The  deep  surface  of  the  gland  is  irregular,  and  moulded  upon 
the  subjacent  parts. 

Thus  it  sends  a  prolongation  which  passes  inwards  between  the  neck  of  the 
mandible  and  the  internal  lateral  ligament ;  another  process  which  passes  in  front 
of  the  styloid  process,  and  e.xtends  upwards  and  occupies  the  posterior  part  of  the 
glenoid  cavity ;  a  third  process  passes  behind  the  styloid  process,  below  the  mastoid 
process  and  behind  the  sterno-mastoid  muscle,  and  sometimes  penetrates  deep 
enough  to  be  in  contact  with  the  internal  jugular  vein. 


58 


PAROTID    GLAND. 


The  internal  carotid  artery  and  internal  jugular  vein  are  in 
contact  with  the  gland  internally. 

On  carefully  removing  the  substance  of  the  parotid  gland,  the 
following  structures  are  seen  in  its  interior,  proceeding  in  the 
order  of  their  depth  from  the  surface  :  — 

1.  Two  or  more  small  lymphatic  glands. 

2.  The  pes  anserinus,  or  primary  branches  of  the  facial  nerve, 
which  emerges  at  its  anterior  border. 


Fig.  22. 

3.  Branches  from  the  great  auricular  and  auriculo-temporal 
nerves  which  communicate  in  its  substance  with  the  facial  nerve. 

4.  The  external  jugular  vein  formed  by  the  junction  of  the 
internal  maxillary  and  temporal  veins. 

5.  The  external  carotid  artery,  which,  after  distributing  many 
branches  to  the  gland,  divides,  opposite  the  neck  of  the  man- 
dible, into  the  internal  maxillary  and  temporal,  the  latter  giving 
off  in  the  gland  the  posterior  auricular  and  tran.sverse  facial 
arteries. 


PORTIO    DURA,    OR    FACIAL    NERVE.  59 

That  portion  of  the  gland  which  lies  on  the  masseter  muscle  is  called  glandiila 
socia  parotiJis.  It  varies  in  size  in  different  subjects  ;  and  is  situated  chiefly 
above  the  parotid  duct,  into  which  it  pours  its  secretion  by  one  or  two  smaller 
ducts. 

The  duct  of  the  paj-otid  gland  (ductus  Stenonis  *),  about  two 
inches  and  a  half  (6.5  c.  in.)  long,  3  mm.  in  diameter,  is  very 
thick  and  strong.  In  this  respect  it  differs  from  the  duct  of  the 
submandibular  gland,  which  is  less  exposed  to  injury.  The  vol- 
ume of  the  parotid  is  26  c.  cm.,  its  weight  is  6.75  drachms  (27 
gm.).  It  runs  transversely  forwards  over  the  masseter,  about 
an  inch  {2.^  c.  vi.)  below  the  zygoma,  through  the  fat  of  the 
cheek,  then  perforates  the  buccinator  obliquely,  and  opens  into 
the  mouth  opposite  the  second  molar  tooth  of  the  maxilla.  Near 
its  termination  it  is  crossed  by  the  zygomaticus  major  and  the 
facial  vein.  After  perforating  the  buccinator,  the  duct  passes 
for  a  short  distance  between  the  muscle  and  the  mucous  mem- 
brane. Its  orifice  is  small  and  contracted  compared  with  the 
diameter  of  the  rest  of  the  duct,  which  will  admit  a  crow-quill ; 
it  is  not  easily  found  in  the  mouth,  being  concealed  by  a  fold  of 
mucous  membrane. 

The  direction  of  the  parotid  duct  ccrresponds  with  a  line 
drawn  from  the  middle  of  the  lobule  of  the  ear  to  a  point  midway 
between  the  nose  and  the  mouth. 

The  blood  supply  of  the  parotid  is  derived  from  the  external 
carotid  and  its  branches,  which  are  accompanied  by  their  respec- 
tive veins.  Its  nerves  are  supplied  from  the  sympathetic  plexus, 
around  the  external  carotid,  the  auriculo-temporal,  the  great 
auricular,  and  the  facial  nerves. 

The  lymphatic  glands  about  the  parotid  deserve  notice,  since  they  are  liable  to 
become  enlarged,  and  simulate  disease  of  the  parotid  itself.  A  lymphatic  gland 
lies  close  to  the  root  of  the  zygoma,  in  front  of  the  cartilage  of  the  ear ;  this  gland 
is  sometimes  affected  in  disease  of  the  external  tunics  of  the  eye;  e.g.,  in  purulent 
ophthalmia;  also  in  affections  of  the  scalp. 

To  display  the  plexus  of  nerves  (pes  anserinus),  formed  by 
the  branches  of  the  facial,  cut  into  the  parotid  gland  by  a  verti- 
cal incision  until  the  main  trunk  of  the  nerve  is  reached. 

Portio  dura,  or  Facial  Nerve. — This  is  the  seventh  cra- 
nial nerve,  and  is  the  motor  nerve  of  the  face.  It  supplies  all 
the  muscles  of  expression,  the  platysma,  and  the  buccinator. 
Through  some  of  its  branches  it  supplies  other  muscles,  the 
description  of  which  will  be  deferred  till  the  facial  nerve  is  dis- 
sected in  the  temporal  bone. 

*  Nic.  Steno,  Dc  GlaminUs  Oris,  etc.     Bat.  1661. 


Go  THE    INFRA-ORBITAL. 

It  arises  immediately  below  the  pons,  from  the  lateral  tract  of  the  medulla 
oblongata,  between  the  olivary  and  restiform, bodies.  The  nerve  enters  the 
meatus  auditorius  intemus,  lying  upon  the  auditory  nerve,  traverses  a  tortuous 
bony  canal  [Aijiicthtcius  Fallopii'\  in  the  petrous  portion  of  the  temporal  bone,  and 
leaves  the  skull  at  the  stylo-mastoid  foramen.  Its  course  and  connections  in  the 
temporal  bone  will  be  studied  hereafter :  at  present  we  must  trace  the  facial  part 
of  the  nerve. 

Having  emerged  from  the  stylo-mastoid  foramen,  the  nerve 
enters  the  parotid  gland,  and  divides  behind  the  ramus  of  the 
mandible  into  two  primary  branches,  named,  from  their  distribu- 
tion, tcniporo-facial  and  cervico-facial.  These  primary  branches 
cross  over  the  external  carotid  artery  and  the  external  jugular 
vein,  and  form,  by  their  communications  within  the  substance  of 
the  parotid,  the  plexus  called /^j-  anserimis,  from  its  fancied  re- 
semblance to  the  skeleton  of  a  goose's  foot  (Fig.  23). 

Close  to  the  stylo-mastoid  foramen,  the  facial  nerve  gi'^es  off 
its  posterior  auricular  branch  (Fig.  23),  which  ascends  behind 
the  ear  and  divides  into  two,  an  auricular  and  an  occipital. 

The  former  supplies  the  retrahens  and  attollens  aurem,  the  latter  the  posterior 
belly  of  the  occipito-frontalis.  This  branch  communicates  with  the  deep  branch 
of  the  great  auricular  n.,  with  the  small  occipital,  and  with  the  auricular  branch  of 
the  pneumogastric.  Its  two  next  branches  supply  the  stylo-hyoideus  and  the 
posterior  belly  of  the  digastric.  The  digastric  nerve  enters  the  muscle  by  many 
filaments;  the  nerve  to  the  stylo-hyoideus  is  long,  and  enters  the  muscle  about 
the  middle.  The  stylohyoid  branch  communicates  with  the  sympathetic  on  the 
external  carotid  a. ;  the  digastric  branch  with  the  glosso-pharyngeal  near  the  base 
of  the  skull.  These  two  muscular  nerves  are  frequently  given  off  from  a  common 
branch. 

The  temporo  facial  division,  the  larger  of  the  two,  in  pass-ing 
through  the  parotid  gland,  crosses  the  external  carotid  and  the 
neck  of  the  mandible,  receives  two  or  more  communications  from 
the  auriculo-temporal  (branch  of  the  fifth),  and  subdivides  into 
temporal,  malar,  and  infra-orbital  branches. 

The  ta7iporal  branches  ascend  over  the  zygoma,  supply  the  frontalis,  the  attra- 
hens  aurem,  the  orbicularis  palpebrarum,  the  corrugator  supercilii,  and  tensor  tarsi, 
and  communicate  with  filaments  of  the  supra-orbital  nerve,  with  the  temporal 
branch  of  the  superior  maxillary  n.  (^sitpra-mandibular),  with  the  auriculo-temporal 
n.,  and  with  the  lachr}'mal  n. 

The  fnaliir  branches  cross  the  malar  bone,  supply  the  orbicular  muscle,  and 
communicate  with  filaments  of  the  lachrymal,  the  supra-orbital,  the  maxillary,  and 
the  malar  branch  of  the  maxillary. 

The  infra-orbital  branches  are  the  largest,  and  proceed 
transversely  forwards  over  the  masseter  beneath  the  zygomatici, 
to  supply  the  orbicularis  oris,  the  elevators  of  the  upper  lip,  and 
the  muscles  of  the  nose. 


THE    FACIAL    NERVE. 


6l 


The  superficial  branches  join  with  the  nasal  and  infra-trochlear  branches  of  the 
ophthalmic  along  the  side  of  the  nose;  the  deep  branches  communicate  beneath 
the  levator  labii  superioris  with  the  infra-orbital  branches  of  the  maxillary  nerve 
forming  the  infra-orbital  plexus,  and  also  with  the  buccal  branches  of  the  facial. 


TPocHieAn 


IHFRATROCHLeAH 


The  cervico  facial  division,  joined  in  the  parotid  gland  by 
filament  from  the  great  auricular  (branch  of  the  cervical  plexus), 
descends  towards  the  angle  of  the  mandible,  and  subdivides  into 
buccal,  supra-  and  infra-maxillary  branches. 


62  SENSORY  NERVES  OF  THE  FACE. 

The  buccal  branches  pass  foi'waids  over  the  niasseter  parallel  with  the  parotid 
duct,  and  supply  the  buccinator ;  they  communicate  with  the  buccal  branch  of  the 
inferior  maxillary  nerve  (third  division  of  the  fifth),  and  with  the  infra-oibital 
nerve. 

The  s^ipra-vi axillary  [supra-mandtbular)  branches  advance  over  the  masseter 
and  facial  artery,  and  run  under  the  platysma  and  the  depressor  muscles  of  the 
lower  lip,  all  of  which  they  supply.  Some  of  the  filaments  communicate  with  the 
mental  branch  of  the  inferior  dental  nerve. 

The  infra  maxillary  {iiifra-niaiiddmlar)  or  cervical  branches,  one  or  more  in 
number,  arch  fonvards  below  the  mandible  covered  by  the  platysma,  as  low  as  the 
hyoid  bone,  and  communicate  with  the  superficial  cervical  (branch  of  the  cervical 
plexus). 

Sensory  Nerves  of  the  Face.  —  These  are  the  supra- 
orbital, the  supra-  and  infra-trochlear,  the  naso-lobular,  the  tem- 
poro-malar,  the  infra-orbital,  and  the  mental,  all  branches  of  the 
fifth  pair. 

The  supra-orbital  nerve  is  the  continuation  of  the  frontal,  which  is  a  branch 
of  the  first  division  of  the  fifth  pair.  It  leaves  the  orbit  through  the  supra  oibital 
notch  and  ascends  upon  the  forehead,  at  first  covered  by  the  orbicularis  and 
occipito-frontalis.  It  presently  divides  into  two  sets  of  branches — 2iV\.  outer,  \\iS. 
larger,  which  passes  backwards  as  far  as  the  occipital  bone,  and  an  inner,  which 
ascends  as  far  as  the  parietal  bone.  It  distributes  sensory  muscular  branches  also 
to  the  orbicularis  palpebrarum,  con'ugator  supercilii,  the  occipito-fiontalis,  to  the 
pericranium,  and  branches  which  supply  the  skin  of  the  forehead,  upper  eyelid, 
and  scalp.  It  communicates  with  the  facial  nerve  on  the  forehead.  The  supra- 
orbital artery  is  a  branch  of  the  ophthalmic. 

The  supra-trochlear  n.,  or  internal  frontal,  appears  at  the  inner  angle  of  the 
orbit  between  the  supra-orbital  foramen  and  the  pulley  of  the  superior  oblique, 
and  sends  down  in  front  of  the  pulley  a  loop  to  communicate  with  the  infra-troch- 
lear branch  of  the  nasal.  The  main  trunk  of  the  nerve  ascends  to  the  foiehead. 
Its  further  course  has  been  described  (p.  23). 

The  ififra-irocklear  n.  issues  from  the  orbit  below  the  pulley,  and  supplies 
branches  to  the  eyelids,  the  conjunctiva,  lachrymal  sac,  and  the  side  of  the  nose. 

The  mfra-orbital  nerve  is  the  terminal  branch  of  the  maxillary 
or  second  division  of  the  fifth  nerve.  It  emerges  with  its  artery 
from  the  infra-orbital  foramen,  covered  by  the  levator  labii 
superioris. 

The  nerve  immediately  divides  into  several  branches,  palpebral,  nasal,  and 
labial;  the  palpebral,  ascending  beneath  the  orbicularis,  supply  the  lower  eyelid, 
and  communicate  with  the  facial  and  the  malar  branch  of  the  orbital  nerve;  the 
nasal  pa.ss  inwards  to  .supply  the  nose,  and  join  the  nasal  branch  (naso-lobular)  of 
the  ophthalmic;  the  labial,  by  far  the  most  numerous,  descend  into  the  upper  lip, 
beneath  the  levator  labii  superioris,  and  eventually  terminate  in  lashes  of  filamenls, 
which  endow  the  papillre  of  the  lip  and  the  mucous  membrane  of  the  mouth  with 
exquisite  sensil)ility.  Close  to  the  infra-orbital  foramen  is  the  infra-orbital  plexus, 
before  alluded  to  (p.  61). 

The  infra-orhital  artery  is  the  terminal  branch  of  the  internal 
ma.xillary  ;  it  supplies  the  muscles,  the  skin,  and  the  front  teeth 
of  the  maxilla,  and  inosculates  with  the  transverse  facial, 
buccal,  facial,  and  coronary  arteries. 


DISSECTION    OF    THE    ORBIT. 


63 


The  naso-lobular  nerve  is  the  external  branch  of  the  nasal  nerve,  and  is  dis- 
tributed to  the  tip  and  lobule  of  the  nose,  and  is  joined  by  filaments  from  the  facial 
nerve. 

The  temporal  branch  of  the  orbital  nerve  (branch  of  the  maxillary  nerve,  run- 
ning along  the  outer  wall  of  the  orbit,  and  which  divides  into  a  temporal  and  a 
malar  branch)  issues  through  the  temporal  fascia  about  a  finger's  breadth  above 
the  zygoma,  and  supplies  the  skin  of  the  temple.  It  communicates  with  the  facial 
and  the  auriculo-temporal  nerves. 

The  tnalar  nerve,  a  branch  also  of  the  orbital  nerve,  issues  through  a  foramen 
in  the  malar  bone,  and,  after  piercing  the  orbicularis  palpebrarum,  supplies  the 
skin  of  the  cheek  over  the  malar  bone.  It  communicates  with  the  facial  and  the 
palpebral  branches  of  the  infra-orbital  nerve. 

third 
in 


mandibular  or 


emerges  from  the  mental  foramen 


The  mental  nerve  is  a  branch  of  the 
division  of  the  fifth.  It 
the  mandible,  in  a  di- 
rection upwards  and 
backwards,  beneath  the 
depressor  anguli  oris.  It 
soon  divides  into  a  num- 
ber of  branches  beneath 
the  depressor  labii  infe- 
rioris,  some  of  which 
supply  the  skin  of  the 
chin,  but  the  greater 
number  terminate  in  the 
papillae  of  the  lower  lip. 
It  communicates  with 
the  facial  nerve. 

The  mental  artery  is  a 
branch  of  the  mandibu- 
lar. It  supplies  the 
gums  and  the  chin,  and 
inosculates  with  the  sub- 
mental, the  inferior  la- 
bial, and  inferior  coro- 
nary arteries. 

Dissection.  —  To  ex- 
pose the  contents  of  the 
orbit,  remove  that  por- 
tion of  the  orbital  plate  which  forms  the  roof  of  the  orbit 
as  far  back  as  the  optic  foramen,  making  one  section  with  a 
saw  on  the  outer  side,  and  the  other  on  the  inner  side  of  the 
roof,  so  that  the  two  sections  converge  at  the  optic  foramen. 
In  doing  this,  be  careful  not  to  injure  the  little  pulley  on  the 
inner  side  of  the  superior  oblique.     If  the  bone  be  sufficiently 


Fig.  24.  —  Diagram  of  the  Sensory  Nerves  of  the 
Scalp  and  Face. 

I.  Great  occipital.  2.  Small  occipital.  3.  Auricular  br. 
of  the  pneumogastric.  4.  Great  auricular.  5.  Auricftto- 
temporal.  6.  Temporal  br.  of  maxillary  nerve.  7.  Supra- 
orbital. 8.  Supra-trochlear.  g.  Malar  br.  of  maxillary 
nerve.  10.  Infra-trochlear.  11.  Naso-lobular.  12.  In- 
fra-orbital.    13.  Buccal  br.  of  nerve.     14.  Mental. 


64  PERIOSTEUM    OF    THE    ORBIT. 

sawn  through,  a  gentle  tap  with  the  saw  on  the  front  of  the 
orbital  plate  will  fracture  its  thin  wall  transversely.  The  an- 
terior fourth  of  the  roof  should  be  turned  forwards  and  down- 
wards and  kept  in  this  position  by  hooks ;  the  remainder  is  to 
be  removed  by  bone  forceps  nearly  as  far  as  the  optic  foramen, 
so  as  to  leave  a  ring  of  bone  from  which  most  of  the  ocular 
muscles  have  their  origin.  The  eyeball  should  be  made  tense 
by  blowing  air  through  a  blowpipe  passed  well  into  the  globe 
through  the  cranial  end  of  the  optic  nerve. 

Periosteum  of  the  Orbit.  —  The  roof  being  removed,  we 
expose  the  fibrous  membrane  which  lines  the  walls  of  the  orbit. 
It  is  a  continuation  of  the  dura  through  the  sphenoidal  fis- 
sure. Traced  forwards,  we  find  that  it  is  loosely  connected 
to  the  walls  of  the  orbit,  and  that  at  the  margin  of  the  orbit  it 
divides  into  two  layers,  one  of  which  is  continuous  with  the  peri- 
osteum of  the  forehead,  the  other  forms  the  broad  tarsal  liga- 
ment which  fixes  the  tarsal  cartilage. 

The  periosteum  is  now  to  be  removed,  and  the  fascia  of  the 
orbit  made  out.  The  following  objects  should  then  be  carefully 
traced  :  in  the  middle  are  seen  \\\&  frontal  artery  and  nerve,  lying 
on  the  levator  palpebrse ;  on  the  outer  side,  the  lacJirymal  nerve 
and  artery  pass  forwards  on  the  external  rectus  to  the  lachrymal 
gland,  which  lies  under  cover  of  the  external  angular  process  ; 
on  the  inner  side  is  \.\\q.  fourth  nerve,  lying  on  and  supplying  the 
superior  oblique. 

Fascia  of  the  Orbit  and  Capsule  of  Tenon.  —  The  fascia 
of  the  orbit  provides  the  lachrymal  gland  and  each  of  the 
muscles  with  a  loose  sheath,  thin  and  delicate  at  the  back  of 
the  orbit,  but  stronger  near  the  eyeball.  It  is  pierced  behind 
by  the  optic  nerve  and  by  the  arteries  and  nerves  of  the  orbit, 
while  in  front  it  is  connected  with  the  ocular  conjunctiva  close 
to  the  cornea.  The  sheaths  are  firmly  adherent  to  the  muscles, 
and  their  tendinous  insertions  into  the  globe  are  connected  by 
the  fascia.  From  the  insertions  of  the  muscles  it  is  reflected 
as  a  double  layer  backwards  over  the  globe,  so  that  it  resembles 
a  serous  membranous  sac  —  a  tunic  vaginalis  —  one  layer  being 
loosely  connected  with  the  globe,  and  extending  back  to  the 
optic  nerve  where  it  is  loose  and  saculated,  the  other  lining  the 
fat  in  which  the  globe  is  set.  These  layers  are  lined  with  epi- 
thelium,  and  internally  it  is  connected  with  the  sclerotic  by  deli- 
cate connective  tissue  {Adventitia  ocnli  Lockwood)  except  around 
the  optic  nerve  entrance  where  it   blends  with  the  sclerotic. 


CONTENTS    OF    THE    ORBIT.  65 

This  reflection  of  the  orbital  fascia  is  called  the  capsule  of  Tenon, 
its  use  being  to  allow  free  movement  of  the  globe,  and  the  in- 
interval  between  the  folds  of  the  capsule  is  known  as  Tenon's 
space. 

The  orbit  contains  a  large  quantity  of  granular  fat,  which  forms 
a  soft  bed  for  the  eye,  and  prevents  its  being  retracted  too  far 
by  its  muscles.  Upon  the  amount  of  this  fat  depends,  in  some 
measure,  the  prominence  of  the  eyes.  Its  absorption  in  disease 
or  old  age  occasions  the  sinking  of  the  eyeballs.  [The  main- 
tenance of  the  eyeball  is  partly  due  to  elastic  ligamentous  struc- 
tures connecting  the  tendons  of  the  internal  and  external  recti 
lachrymal  and  malar  bones,  known  as  cJieck  ligaments.     A.  H.] 


Fig.  25.  —  Diagram  of  the  Nerves  of  the  Orhit. 

Contents  of  the  Orbit.  —  In  the  middle  of  the  orbit  is  the 
eyeball,  surrounded  by  more  or  less  fat,  and  attached  to  it  are 
six  muscles  which  move  it :  four,  running  forwards  in  a  straight 
direction,  are  called  the  recti,  and  are  arranged  one  above,  one 
below,  and  one  on  each  side  of  the  globe  ;  the  remaining  two  are 
called,  from  their  direction,  obliqui,  one  superior,  the  other  in- 
ferior. There  is  also  a  muscle  to  raise  the  upper  eyelid,  termed 
levator palpebrcB.  The  nemcs  are  :  the  optic,  which  passes  through 
the  optic  foramen ;  the  third,  the  fourth,  the  first  division  of  the 
fifth,  the  sixth,  and  some  filaments  of  the  sympathetic,  all  of 
which  pass  through  the  sphenoidal  fissure.  The  third  supplies 
all  the  muscles  with  motor  power,  except  the  superior  oblique, 
which  is  supplied  by  the  fourth,  and  the  external  rectus,  which 


66  FRONTAL    NERVE. 

is  supplied  by  the  sixth.  The  first  or  ophthalmic  division  of 
the  fifth  divides  into  a  frontal,  lachrymal,  and  nasal  branch. 
The  ophthalmic  artery,  a  branch  of  the  internal  carotid,  passes 
into  the  orbit  through  the  optic  foramen  ;  its  vein  passes  back- 
wards through  the  sphenoidal  fissure  to  join  the  cavernous  sinus. 
Frontal  Nerve.  —  The  ophthalmic,  or  first  division  of  the 
fifth  —  a  sensory  nerve  —  after  giving  off  from  its  inner  and 
lower  side,  whilst  within  the  cavernous  sinus,  the  nasal  nerve, 
divides  into  the  frontal  and  lachrymal  nerves,  of  which  the  former 
is  the  larger. 

It  is  the  smallest  division  of  the  fifth,  and  runs  forv\-ards  for  the  distance  of 
about  an  inch  (2.5  c.  m.) ;  in  its  course  it  is  connected  with  the  cavernous  plexus 
of  the  s}'mpathetic,  with  the  third,  fourth,  and  sixth  nerves,  and  close  to  its  origin 
from  the  Gasserian  ganglion  it  sends  off  a  small  recurrent  branch  to  the  tentorium. 

One  of  its  divisions,  the  frontal  nerve,  runs  forwards  upon  the 
under  surface  of  the  levator  palpebrae,  on  which,  about  midway 
in  the  orbit,  it  divides  into  two  branches  —  the  supra-trochlear 
and  the  supra-orbital. 

a.  The  supra-trochlear,  the  smaller  of  the  two  (Fig.  26,  p.  67)  runs  obliquely  in- 
wards above  the  pulley  of  the  superior  oblique  to  the  inner  angle  of  the  orbit.  Here 
it  gives  off  a  small  communication  downwards  to  the  infra-trochlear  branch  of  the 
nasal,  and  then  divides,  after  passing  between  the  bone  and  the  orbicularis  pal- 
pebrarum, into  filaments  which  supply  the  skin  of  the  upper  eyelid,  forehead,  and 
nose.  One  or  two  small  filaments  may  be  traced  through  the  bone  to  the  mucous 
membrane  of  the  frontal  sinuses. 

b.  The  supra-orbital  is  the  continuation  of  the  frontal  nerve, 
and  runs  forwards  on  the  levator  palpebrae  to  the  supra-orbital 
notch,  through  which  it  ascends  to  supply  the  skin  of  the  upper 
eyelid,  forehead,  pericranium,  and  scalp.  Its  cutaneous  branches, 
an  inner  and  an  outer,  which  run  upwards  beneath  the  occipito- 
f  rontalis,  have  been  described  in  the  dissection  of  the  scalp  (p.  23). 
It  supplies  with  common  sensation  the  orbicularis  palpebrarum, 
the  occipito-frontalis,  and  the  corrugator  supercilii,  where  it 
joins  the  facial  nerve. 

Lachrymal  Nerve.  —  This  is  the  smallest  of  the  three 
branches  of  the  ophthalmic  nerve.  It  runs  along  the  upper 
border  of  the  external  rectus  on  the  outer  side  of  the  orbit  with 
the  lachrymal  artery,  through  the  lachrymal  gland,  which  it  sup- 
plies as  well  as  the  upper  eyelid.  Its  branches  within  the  orbit 
are:  i,  a  branch  which  passes  down  behind  the  lachrymal  gland 
to  communicate  with  the  orbital  branch  of  the  maxillary  nerve ; 
2,  filaments  to  the  lachrymal  gland.  It  then  pierces  the  pal- 
pebral ligament  to  supply  the  skin  of  the  upper  eyelid. 


LACHRYMAL    GLAND. 


^7 


Fourth  Cranial  Nerve.  —  This  nerve  enters  the  orbit 
through  the  sphenoidal  fissure  above  the  other  nerves.  It  runs 
along  the  inner  side  of  the  frontal  nerve,  and  enters  the  upper 
or  orbital  surface  of  the  superior  oblique,  to  which  it  is  solely 
distributed.  This  nerve  is  joined  in  the  outer  wall  of  the  caver- 
nous sinus  by  filaments  from  the  sympathetic.  It  communi- 
cates occasionally  with  the  lachrymal,  and  the  ophthalmic  divis- 
ion of  the  fifth.  Here  also  it  sends  backwards  two  or  more 
filaments  to  supply  the  tentorium  cerebelli. 


IN  FRA-TROCHLE AR 

,,    „  SUPRA-ORBITAI. 


SUPRA- 
TROCHLE  AR 


OPTIC 

Fig.  26.  —  View  of  Orbit  from  Above. 


Lachrymal  Gland.  —  This  gland  is  situated  below  the  ex- 
ternal angular  process  of  the  frontal  bone.  It  consists  of  an 
orbital  and  palpebral  portion  —  the  former  placed  beneath  the 
external  angular  process  of  the  frontal  bone  in  a  depression  for 
its  reception,  the  latter  extending  to  the  margin  of  the  upper 
lid.  The  orbital  portion  is  oval,  flattened,  and  curved,  is  held 
in  place  by  a  suspensory  ligament  attached  to  the  bone,  and  ex- 
tends one-fifth  of  the  distance  into  the  orbital  cavity  from  this 
base.  It  is  %  of  an  inch  (19  mm.)  from  before  backwards,  %. 
inch  (13  mm.)  wide,  \  of  an  inch  (3  mm.)  thick,  and  weighs  .8 
of  a  gm.,  and  has  a  volume  of  about  0.66  cm.  It  is  limited  ex- 
ternally by  the  external  palpebral  ligament,  internally  by  the 
edge  of  the  superior  rectus.  The  palpebral  portion  is  quadri- 
lateral, smaller,  thinner,  and  is  in  contact  with  the  palpebral 
conjunctiva.  It  is  K  of  an  inch  (9  mm.)  long,  nearly  as  wide, 
and  yV  of  an  inch  (2  mm.)  thick.      The  lachrymal  gland  empties 


68 


LEVATOR    PALPEBRAE. 


by  ten  to  fifteen  excretory  ducts  which  run  parallel  and  per- 
forate the  conjunctiva  in  a  row  on  the  upper  lid  %  of  an  inch 
(6.5  mm.)  above  the  tarsal  cartilage  near  the  external  canthus. 
They  are  not  easily  discovered  in  the  human  eye ;  in  that  of 
the  horse  or  bullock  they  are  large  enough  to  admit  a  small 
probe.  The  secretion  of  the  gland  keeps  the  surface  of  the 
cornea  constantly  moist  and  poUshed  ;  but  if  dust,  or  any  for- 
eign substance,  irritate  the  eye,  the  tears  flow  in  abundance 
and  wash  it  off. 


Fig.  27.  —  Lachrymal  Gland. 


7,  7.  Orbital  portion  of  the  lachrymal  gland.  8,  9,  10.  Palpebral  portion  of  this  gland. 

II,  II.  Mouths  of  its  excretory  ducts. 


All  the  muscles  of  the  orbit,  with  the  exception  of  the  infe- 
rior oblique,  arise  from  the  margin  of  the  foramen  opticum,  and 
pass  forwards,  like  ribbons,  to  their  insertions. 

Levator  Palpebrae. — This  muscle  arises  from  the  roof  of 
the  orbit,  above  and  in  front  of  the  optic  foramen,  and  above  the 
origin  of  the  superior  rectus.  It  gradually  increases  in  breadth, 
and  terminates  in  a  broad,  thin  aponeurosis,  which  is  inscited 
into  the  upper  surface  of  the  tarsal  cartilage  by  a  broad  aponeu- 
rosis. It  is  constantly  in  action  when  the  eyes  are  open,  in 
order  to  counteract  the  tendency  of  the  lids  to  fall.  It  is,  from 
its  position  and  origin,  closely  associated  with  the  superior  rec- 
tus ;  its  action  involves  that  of  the  rectus  superior  as  well. 
"  Hansell  &  Reber  "  (Muscular  Anomalies  of  the  Eye).  As  sleep 
approaches,  the  muscle  relaxes,  the  eyes  feci  heavy,  and  the  lids 


OBLIQUUS    SUPERIOR. 


69 


close.     Its  nerve  comes  from  the  superior  division  of  the  third 
nerve,  and  enters  it  on  its  under  or  ocular  aspect. 

Obliquus  Superior.  —  This  muscle  arises  from  the  inner 
side  of  the  optic  foramen.  It  runs  forwards  along  the  inner  and 
upper  side  of  the  orbit,  and  terminates  in  a  round  tendon,  which 
passes  through  a  fibro-cartilaginous  loop  —  trocJilca  —  attached 
to  the  trochlear  fossa  in  the  frontal  bone.  From  the  loop  the 
tendon  is  reflected  backwards,  downwards,  and  outwards  at  an 
angle  of  53°  with  the  first  portion  of  the  muscle,  beneath  the 
superior  rectus,  and  is  inserted  by  an  expanded  tendon  into  the 
outer  part  of  the  sclerotic  coat,  midway  between  the  cornea 
and  the  entrance  of  the  optic  nerve,  16  mm.  from  the  limbus. 
The  loop  is  lined  by  a  synovial  membrane,  which  is  continued 


Fig.  28. —  Muscles  of  the  Eye.    Ligament  of  Zinn. 

1.  Attachment  of  the  ligament  of  Zinn  — showing  the  three  tongue-like  projections,  from  its  annu- 
lar parts  surrounding  the  optic  nerve,  to  the  Internal,  external,  and  mferior  recti  muscles 
2.  External  rectus,  incised  and  deflected  downwards  to  show  the  internal  rectus.  3.  Internal 
rectus.  4.  Inferior  rectus.  5.  Superior  rectus.  6.  Superior  oblique,  7.  Pulley  for  the 
superior  oblique  muscle.  8.  Inferior  oblique.  9.  Levator  palpebrse.  10.  Portion  of  the 
orbicularis  palpebrarum.     11.    Optic  nerve. 

over  the  tendon.  The  action  of  this  muscle  will  be  considered 
with  that  of  the  inferior  oblique.  It  is  supplied  by  the  fourth 
nerve,  which  enters  the  back  part  of  its  upper  surface. 

The  frontal  nerve  and  levator  palpebrae  are  now  to  be  cut 
through  the  middle  and  reflected,  the  front  part  forwards  and 
the  hind  part  backwards.  On  its  under  aspect  is  seen  the  twig 
from  the  upper  division  of  the  third  nerve  entering  it.  On  re- 
flecting this  muscle  the  superior  rectus  is  exposed. 

The  superior  rectus  arises  by  a  tendinous  origin  from  the  upper 


•JO  NASAL    NERVE. 

margin  of  the  optic  foramen  and  from  the  sheath  of  the  optic 
nerve,  and  is  inserted  by  a  broad,  thin  tendon  (which  invaginates 
Tennon's  capsule)  into  the  sclerotic  coat.  This  tendon  is  in- 
serted anterior  to  the  equator  of  the  globe,  and  8  mm.  posterior 
to  the  corneo-scleral  border;  is  5.8  mm.  long.  The  largest  area 
of  the  muscle  on  cross  section  is  ii.X  mm.,  and  its  length  is 
41.8  mm.      (Hansell  &  Reber.) 

Action.  —  "It  controls  the  upper  half  of  the  field  of  fixation, 
turns  the  eye  vertically  up,  this  vertical  movement  increasing 
as  the  eye  is  abducted,  and  diminished  as  the  eye  is  adducted  ; 
it  also  rotates  the  cornea  horizontally  nasalwards,  and  tiJts  the 
upper  end  of  the  cornea  in,  more  in  adduction,  less  in  ab- 
duction."    Hansell  &  Reber. 

Dissection.  —  Reflect  this  muscle  by  cutting  through  the 
middle,  and,  in  doing  so,  observe  a  filament  from  the  third  nerve 
entering  its  under  aspect.  After  the  removal  of  a  quantity  of 
granular  fat,  the  follow^ing  objects  are  exposed  :  beneath  the 
muscle  are  the  optic  nerve,  the  ophthalmic  artery  and  vein,  the 
nasal  nerve  and  its  ciliary  branches  crossing  over  the  optic 
nerve,  and  further  forwards  is  the  reflected  tendon  of  the  supe- 
rior oblique  ;  on  the  outer  side  of  the  optic  nerve,  and  close  to 
the  ophthalmic  artery,  is  the  lenticular  ganglion,  with  numerous 
ciliary  filaments  passing  forwards  from  it  to  enter  the  sclerotic. 
The  student  should  now  trace  backwards  the  two  roots  which 
enter  the  upper  and  lower  angle  respectively  of  the  ganglion, 
the  upper  being  its  sensory  branch  from  the  nasal,  the  lower  its 
motor  root  from  the  lower  division  of  the  third  nerve.  Further 
back  should  be  traced  the  third,  the  nasal  branch  of  the  oph- 
thalmic, and  the  sixth  nerves  passing  between  the  two  heads 
of  the  external  rectus  to  their  respective  destinations.  The 
ophthalmic  artery  and  its  branches  may  also  at  this  stage  be 
exposed  and  cleaned. 

Nasal  Nerve.  —  This  is  one  of  the  three  divisions  of  the 
ophthalmic  branch  of  the  fifth,  and  is  usually  the  first  branch 
given  off  (Fig.  25,  p.  65).  It  enters  the  orbit  through  the 
sphenoidal  fissure  between  the  two  origins  of  the  external  rec- 
tus, and  between  the  two  divisions  of  the  third  n.  It  then 
crosses  obliquely  over  the  optic  nerve,  beneath  the  levator  pal- 
pebrae  and  the  superior  rectus,  towards  the  inner  wall  of  the 
orbit.  After  giving  off  the  infra-trocJilear  branch,  the  nerve 
passes  out  of  the  orbit  between  the  superior  oblique  and  the  in- 
ternal rectus,  through  the  anterior  ethmoidal  foramen,  into  the 


OPTIC    NERVE. 


71 


cranium,  where  it  lies  beneath  the  dura,  upon  the  cribri- 
form plate  of  the  ethmoid  bone.  It  soon  leaves  the  cranium 
through  the  nasal  slit  near  the  crista  galli,  and  enters  the  nose. 
Here  it  divides  into  two  branches  —  an  inner  or  septal,  which 
supplies  the  mucous  membrane  of  the  front  of  the  septum  ;  and 
an  outer,  the  main  continuation  of  the  nerve  —  which  runs  in  a 
groove  on  the  under  surface  of  the  nasal  bone,  and  distributes 
branches  to  the  pituitary  membrane  of  the  outer  part  of  the 
nose  and  the  two  lower  turbinated  bones  ;  it  also  gives  off  a 
superficial  branch,  which  emerges  between  the  nasal  bone  and 
the  cartilage,  under  the  name  of  the  naso-lobniar,  and  is  dis- 
tributed to  the  skin  of  the  tip  and  ala  of  the  nose  (Fig.  24,  p.  65). 
The  nasal  nerve  gives  off  the  following  branches  in  the  orbit : 


INT.TROCHLEAR 


Fig.  29.  —  View  of  Optic  and  Lower  Nerves  of  Orbit. 


a.  One  slender  filament  to  \\\.e:  lenticular  ganglion  (forming  its  upper  or  long 
root)  is  given  off  from  the  nasal  nerve  as  it  passes  between  the  heads  of  the  ex- 
ternal rectus  close  to  the  optic  nerve.  It  is  about  half  an  inch  long,  and  enters 
the  posterior-superior  angle  of  the  ganglion. 

b;  Two  or  three  long  ciliary  nerves.  They  run  along  the  inner  side  of  the 
optic  nerve  to  the  back  of  the  globe  of  the  eye.  They  are  joined  by  filaments 
from  the  lenticular  ganglion,  and  pass  through  the  sclerotic  coat  to  supply  the  iris 
(Fig.  29). 

c.  Infra-trocJilear  nerve.  —  This  runs  forwards  along  the  inner  side  of  the  orbit, 
below  the  loop  of  the  superior  oblique,  where  it  communicates  with  the  supra- 
trochlear branch  of  the  frontal  nerve.  It  passes  to  the  inner  angle  of  the  orbit, 
and  divides  into  filaments,  which  supply  the  skin  of  the  eyelids,  the  caruncle,  the 
lachrymal  sac,  and  the  sides  of  the  nose. 

Optic  Nerve.  —  This  nerve,  having  passed  through  the 
optic  foramen,  proceeds  forwards  and  a  little  outwards  for 
about  an  inch  to  the  globe  of  the  eye,  which  it  enters  on  the 


72  OPHTHALMIC    ARTERY. 

nasal  side  of  its  axis.  It  pierces  the  sclerotic  and  choroid  coats, 
and  then  expands  to  form  the  retina.  The  nerve  is  invested 
by  a  dense  fibrous  coat  derived  from  the  dura,  and  by  a  thin 
one  from  the  arachnoid,  both  of  which  pass  forward  as  far  as 
the  sclerotic.  At  the  optic  foramen  it  is  surrounded  by  the 
tendinous  origins  of  the  recti ;  in  the  rest  of  its  course,  by  loose 
fat  and  by  the  ciliary  nerves  and  arteries.  It  is  pierced  in  its 
course  through  the  orbit  by  the  arteria  centralis  retinae,  which 
runs  along  with  its  vein  in  the  middle  of  the  nerve  to  the 
eyeball.* 

Ophthalmic  Artery.  — This  artery  arises  from  the  internal 
carotid,  close  by  the  anterior  clinoid  process.  It  enters  the 
orbit  through  the  optic  foramen,  outside  and  below  the  optic 
nerve ;  occasionally  through  the  sphenoidal  fissure.  Its  course 
in  the  orbit  is  remarkably  tortuous.  Situated  at  first  on  the 
outer  side  of  the  optic  nerve,  it  soon  crosses  over  it,  and  runs 
along  the  inner  side  of  the  orbit  between  the  superior  and  inter- 
nal recti,  to  inosculate  with  the  internal  angular  artery  (the 
terminal  branch  of  the  facial).  Its  branches  arise  in  the  follow- 
ing order :  — 

a.  Lachrymal  Artery.  —  This  branch  proceeds  along  the  outer  wall  of  the  orbit 
above  the  external  rectus,  in  company  with  the  nerve  of  the  same  name,  to  the 
lachrymal  gland.  After  supplying  the  gland,  it  terminates  in  the  conjunctiva  and 
eyelids.  In  the  orbit  it  gives  off  some  malar  branches  which  pierce  the  malar 
bone  to  get  to  the  temporal  fossa,  and  anastomose  with  the  deep  temporal  arteries. 
It  also  sends  a  branch  backwards  through  the  sphenoidal  fissure  to  anastomose 
with  the  arteria  meningea  media  or  midi  duralis. 

b.  Supra-orbital  Artery.- — This  branch  runs  fonvards  with  the  frontal  nerve 
under  the  roof  of  the  orbit  and  upon  the  levator  palpebras.  It  emerges  on  the 
forehead  through  the  supra-orbital  foramen,  where  it  communicates  with  the  super- 
ficial temporal,  frontal,  and  angular  arteries. 

c.  Arteria  Centralis  Retina.  —  This  small  branch  enters  the  optic  nerve  ob- 
liquely on  the  outer  aspect  close  to  the  optic  foramen.  It  runs  in  the  centre  of 
this  nerve  to  the  interior  of  the  eye. 

d.  Ciliary  Arteries.  —  These  branches  may  be  arranged  in  three  groups.  The 
short  ciliary,  twelve  to  fifteen  in  number,  proceed  tortuously  forward  with  the  optic 
nerve,  and  pierce  the  sclerotic  coat  at  the  back  of  the  eye  to  supply  the  choroid 
coat  and  the  iris.  The  long  ciliary,  two  in  number,  run  on  each  side  of  the  optic 
nerve,  enter  the  sclerotic,  and  pass  horizontally  forward,  one  on  each  side  of  the 
globe,  belween  the  sclerotic  and  the  choroid,  neariy  as  far  as  the  iris,  where  each 
divides  into  an  upper  and  a  lower  branch.  These  branches  of  the  two  longciliaiy 
arteries  anastomose  with  the  anterior  ciliary  and  form  two  vascular  circles,  an 
ou'er  at  the  circumference  of  the  iris,  the  circuliis  major,  and  an  inner  at  the  free 
margin  of  the  iris,  the  circulus  minor.  The  anterior  ciliary  are  branches  of  the 
muscular  and  lachrymal  arteries  and  proceed  with  the  tendons  of  the  recti,  and 
enter  the  front  part  of  the  sclerotic  coat.  In  inflammation  of  the  iris  the  vascular 
zone  round  the  cornea  arises  from  enlargement  and  congestion  of  the  anterior 
ciliary  arteries. 

*  A  small  branch  from  Meckel's  ganglion,  ascending  through  the  spheno-maxil- 
lary  fissure,  is  described  by  Arnold  as  joining  tlie  ojjtic  nerve. 


OPHTHALMIC    VEINS.  73 

e.  Ethmoidal  Arteries.  —  Of  these  arteries,  two  in  number,  the  anterior  and  larger 
passes  through  the  anterior  ethmoidal  foramen  with  the  nasal  nerve  ;  the  posterior 
enters  the  posterior  ethmoidal  foramen  with  the  sphenoethmoidal  nerve.  The 
anterior  gives  off  branches  to  the  frontal  and  anterior  ethmoidal  cells,  and  a  nasal 
branch  to  the  nose ;  it  likewise  gives  off  an  anterior  meningeal  branch  to  the  dura 
in  the  anterior  fossa.  The  posterior  is  distributed  to  the  posterior  ethmoidal 
cells  and  upper  part  of  the  nose. 

f.  Muscular  Branches.  —  There  is  an  upper  and  a  lower  branch  supplying  re- 
spectively the  upper  and  lower  muscles :  besides  these,  there  are  irregular  branches 
from  the  lachrymal  and  supra-orbital  arteries. 

g.  Palpebral  Arteries.  —  These  branches,  a  superior  and  an  inferior,  proceed 
from  the  ophthalmic  artery  near  the  front  of  the  orbit.  They  are  distributed  to 
their  respective  eyelids,  forming  arches  near  the  margins  of  the  lids  between  the 
tarsal  cartilages  and  the  orbicularis  palpebrarum,  with  branches  from  the  lachrymal 
and  the  infra  orbital  arteries. 

h.  Nasal  Artery.  —  This  branch  may  be  considered  one  of  the  terminal  divis- 
ions of  the  ophthalmic.  It  leaves  the  orbit  on  the  nasal  side  of  the  eye  above 
the  tendon  of  the  orbicularis,  and  inosculates  with  the  angular  and  nasal  arteries 
of  the  facial.     It  supplies  the  side  of  the  nose  and  the  lachrymal  sac. 

/.  Frontal  Artery.  —  This  is  the  other  terminal  branch  of  the  ophthalmic.  It 
emerges  at  the  inner  angle  of  the  eye,  ascends,  and  inosculates  with  the  supra- 
orbital artery.  [The  arteries  of  the  orbit  are  noted  for  their  twisted  and  contorted 
appearance ;  this  taken  together  with  the  mass  of  fat  in  which  they  are  lodged 
allows  mobility  of  the  eyeball  and  prevents  injury  to  these  vessels.     A.  H.] 

Ophthalmic  Veins.  —  There  are  two  ophthalmic  veins.  The 
superior  commences  at  the  inner  angle  of  the  eye  by  a  commu- 
nication with  the  frontal  and  angular  veins.  It  runs  backwards 
above  the  optic  nerve  in  a  straighter  course  than  the  artery, 
receives  the  veins  corresponding  to  the  arteries  of  the  upper 
and  inner  part  of  the  orbit,  and  finally  passes  between  the  two 
heads  of  the  external  rectus,  through  the  inner  part  of  the 
sphenoidal  fissure,  to  terminate  in  the  cavernous  sinus.  The 
inferior  opJitJialniic  vein  is  formed  by  the  union  of  branches  from 
the  lower  and  outer  part  of  the  orbit,  and  proceeding  backwards 
along  the  floor  of  the  orbit,  opens  into  the  superior  vein,  or 
directly  into  the  cavernous  sinus.  In  front  it  sends  a  commu- 
nicating vein  through  the  spheno-maxillary  fissure  to  join  the 
pterygoid  plexus. 

Ophthalmic  or  Lenticular  Ganglion.  —  This  small  ganglion,*  of  reddish 
color  and  about  the  size  of  a  pin's  head,  is  situated  at  the  back  of  the  orbit, 
between  the  optic  nerve  and  the  external  rectus,  on  the  outer  side  of,  and  usually 
closely  adherent  to,  the  ophthalmic  artery.  It  is  somewhat  quadrilateral  in  shape, 
and  receives  its  sensory  or  long  root  from  the  nasal  nerve,  which  joins  its  posterior 
superior  angle;  its  motor  or  short  root,  from  the  branch  of  the  third  nerve,  going 
to  the  inferior  oblique,  which  enters  its  posterior  inferior  angle ;  and  its  sympa- 
thetic root  from  the  cavernous  plexus  which  joins  it  at  its  posterior  border^  or  in 

*  W.  Marshall  regards  this  ganglion,  from  its  mode  of  development  and  from 
its  relations  in  some  of  the  lower  vertebrates,  to  be  connected  more  with  the  third 
nerve  than  the  ophthalmic. 


74  THIRD  NERVE,  MOTOR  OCULI. 

conjunction  with  its  sensory  root.  The  ganglion,  thus  furnished  with  motor,  sen- 
sory, and  sympathetic  roots,  gives  off  the  short  ciliary  iwrvcs.  These,  from  eight 
to  twelve  in  number,  issue  from  the  anterior  upper  and  lower  angles  of  the  gan- 
glion, usually  four  or  five  from  the  upper,  the  remainder  from  the  lower.  They 
run  very  tortuously  with  the  optic  nerve,  pass  through  the  back  of  the  sclerotic 
coat,  where  they  are  joined  by  the  long  ciliary  (from  the  nasal),  and  are  distributed 
to  the  iris  and  the  ciliary  muscle.  Since  the  ciliary  nerves  derive  their  motor 
influence  from  the  third  nerve,  the  iris  must  lose  its  power  of  contraction  when 
this  nerve  is  paralyzed. 

Third  Nerve,  Motor  Oculi.  — The  third  nerve  passes  for- 
wards in  the  outer  wall  of  the  cavernous  sinus,  and  here  receives 
one  or  two  filaments  from  the  cavernous  plexus  of  the  sympa- 
thetic. Just  before  it  enters  the  inner  end  of  the  sphenoidal 
fissure  it  divides  into  two  branches,  both  of  which  pass  between 
the  two  heads  of  origin  of  the  external  rectus,  separated  from 


Fig.  30.  —  Di.^GRAM  of  the  Nerves  of  the  Orbit. 

each  other  by  the  nasal  nerve.  The  upper  and  smaller  division 
has  been  already  traced  into  the  superior  rectus  and  levator 
palpebrae.  The  lower  division  after  a  short  course  divides  into 
three  branches,  one  passing  inwards  under  the  optic  nerve  to 
supply  the  internal  rectus,  another  passes  to  the  inferior  rectus, 
and  a  third  runs  along  the  floor  of  the  orbit  to  the  inferior 
oblique.  This  last-named  branch  sends  a  small  twig  upwards 
to  the  lenticular  ganglion,  mentioned  in  the  description  of  this 
ganglion,  and  another  to  the  inferior  rectus. 

What  is  the  result  of  paralysis  of  the  third  nerve  ?  Falling 
of  the  upp6r  eyelid  (ptosis),  external  squint,  dilatation  and 
immobility  of  the  pupil. 


RFXTI    MUSCLES.  75 

Sixth  Nerve,  Abducens.  —  This  nerve  lies  in  the  inner 
wall  of  the  cavernous  sinus  external  to  the  internal  carotid 
artery,  passes  through  the  sphenoidal  fissure,  and  enters  the 
orbit  between  the  two  heads  of  the  external  rectus.  Here  it 
lies  below  the  lower  division  of  the  third  and  above  the  ophthal- 
mic vein.  The  nerve  terminates  in  fine  filaments,  which  are 
distributed  to  the  ocular  surface  of  the  external  rectus.  In  the 
cavernus  sinus  it  is  joined  by  filaments  from  the  carotid  plexus, 
and  in  the  orbit  by  a  branch  from  Meckel's  ganglion  and  from 
the  ophthalmic  nerve. 

Respecting  the  motor  nerves  in  the  orbit,  observe  that  they 
all  enter  the  ocular  surface  of  the  muscles,  with  the  exception 
of  the  fourth,  which  enters  the  orbital  surface  of  the  superior 
oblique.      (Fig.  31.) 


Superior  rectus 
FOURTH  NERVE 


Lachrymal  and  frontal  vein 


Levator  palpsbrse  Buperioris 


^^5n  T;^""  Superior  oblique 


Origin    of    external   rectus  from    fibrous -^=^i#x^  V^/il — ■  OPTIC  FORAMEN  AND  NERVE 

bridge  over  sphenoidal  fissure  ^_JC^  ^ —      If 

Naso-cUiary  of  fijth  nerve "Z^^  %^         Internal  rectus 

SIXTH  NERVE """"^      /  ^'"^C^^      N.  ,  , 

/  1  ^  Inferior  rectus 

External  rectus       THIRD  NER  VE 

Fig.  31. — Diagrammatic  Representation  of  Origins  of  Ocular  Muscles  at  the 
Apbx  of  the  Right  Orbit.     (After  Schwalbe  slightly  altered.) 

Recti  Muscles.  —  The  hitcrnal  and  i}ifcrior  recti  arise  from 
a  fibrous  band  — the  ligament  of  Zinn  —  attached  to  the  inner 
and  lower  borders  of  the  optic  foramen.  The  external  rectiis 
arises  by  two  heads,  the  lower  from  the  ligament  of  Zinn  and 
.  the  lower  border  of  the  sphenoidal  fissure,  the  upper  from  the 
margin  of  the  foramen  opticum  ;  between  these  heads  pass  in 
the  following  order,  from  above  downward  —  the  upper  division 
of  the  third,  the  nasal,  the  lower  division  of  the  third,  the  sixth 
nerves,  and  the  ophthalmic  vein.  Its  tendon  invaginates  Te- 
non's capsule  and  is  inserted  by  a  tendon  3.7  mm.  in  length,  in 
vertical  line  7  mm.  from  the  corneo-scleral  junction,  or  liinbiis, 
into  the  sclera.  The  thickest  area  of  the  muscle  is  16.73  mm. 
Its  length  40.6  mm.     (Hansell  and  Reber.) 

Action.  —  It  controls  the  outer  half  of  the  field  of  fixation 
and  rotates  the  cornea  horizontally  temporal-wards.  It  has  no 
action  in  tilting  the  upper  end  of  the  vertical  meridian  of  the 
cornea  either  inwards  or  outwards.      (Hansell  and  Reber.) 


'jd  INFERIOR    RECTUS. 

The  four  recti  diverge  from  each  other,  one  above,  one  below, 
and  one  on  each  side  of  the  optic  nerve. 

Internal  Rectus.  —  The  internal  rectus  arises  by  a  tendon 
common  to  it  and  the  inferior  rectus  from  the  inner  margin  of 
the  optic  foramen,  passes  forward,  lying  close  to  the  inner  wall 
of  the  orbit,  and  is  inserted  into  the  sclera  by  a  tendon  (which 
invaginates  Tenon's  capsule),  8.8  mm.  in  length,  in  the  vertical 
line  10.3  mm.,  and  6.5  mm.  from  the  corneo-scleral  junction,  or 
livibns.  Action. —  It  controls  the  inner  half  of  the  field  of  fixa- 
tion, rotates  the  cornea  horizontally  nasal-wards,  and  has  no 
torsional  action.  The  thickest  area  of  the  muscle  on  horizontal 
section  is  17.39  mm.,  and  its  length  is  40.8  mm.  (Hansell  and 
Reber.) 

Inferior  Rectus.  —  The  inferior  rectus  arises  immediately 
below  the  optic  foramen  in  the  most  internal  part  of  the  sphe- 
noidal fissure  by  a  tendon  common  to  it  and  the  internal  rectus. 
It  lies  close  to  the  floor  of  the  orbit,  and  is  inserted  by  a  tendon 
which  invaginates  Tenon's  capsule  into  the  sclera  8  mm.  from 
the  corneo-scleral  junction  or  limbns.  This  tendon  is  5.8  mm. 
in  length,  in  the  horizontal  line  10.6  mm.  The  largest  area 
of  the  muscle  on  section  is  11^  mm.,  and  its  length  41.8  mm. 
Action.  —  It  controls  the  lower  half  of  the  field  of  fixation, 
turning  the  eye  vertically  down  ;  the  vertical  movement  increas- 
ing with  adduction,  diminishing  with  abduction  ;  it  also  turns 
the  eye  laterally  in,  and  rotates  the  upper  end  of  the  vertical 
meridian  of  the  cornea  out,  these  effects  increasing  as  the  eye 
is  adducted,  decreasing  as  it  is  abducted.      (Hansell  and  Reber.) 

The  recti  muscles  enable  us  to  direct  the  eye  towards  differ- 
ent points.  It  is  obvious  that  by  the  single  action  of  one,  or 
the  combined  action  of  two,  the  eye  can  be  turned  towards  any 
direction. 

The  rectus  superior  is  supplied  by  the  upper  division  of  the 
third  nerve  ;  the  rectus  internus,  the  rectus  inferior,  and  obli- 
quus  inferior,  by  the  lower  division.  The  rectus  externus  is 
supplied  by  the  sixth. 

Follow  the  recti  to  the  eye,  in  order  to  see  the  tendons  by 
which  they  are  inserted.  Notice  also  the  anterior  ciliary  arte- 
ries, which  run  to  the  eye  along  the  tendons.  The  congestion 
of  these  little  vessels  occasions  the  red  zone  round  the  cornea 
in  iritis.  It  has  been  already  mentioned  that  the  tendons  are 
invested  by  a  fascia,  which  passes  from  one  to  the  other,  form- 
ing a  loose  tunic  —  capsule  of  Tenon  — over  the  back  of  the 


INI'ERIOR    OBLIQUE.  7/ 

eye.  This  tunic  consists  of  two  layers  with  an  intermediate 
space,  lined  with  flat  cells,  thus  allowing  free  mobility  of  the 
globe.  It  is  this  fascia  which  resists  the  passage  of  the  hook 
in  the  operation  for  the  cure  of  squinting.  Even  after  the  com- 
plete division  of  the  tendon  the  eye  may  still  be  held  in  its 
faulty  position  if  this  tissue,  instead  of  possessing  its  proper 
softness  and  pliancy,  happen  to  have  become  contracted  and 
unyielding.  Under  such  circumstances  it  is  necessary  to  divide 
it  freely  with  the  scissors. 

By  removing  the  conjunctival  coat  of  the  eye,  the  tendons  of 
the  recti  are  soon  exposed.  The  breadth  and  the  precise  situa- 
tion of  their  insertion  deserve  attention  in  reference  to  the 
operation  for  strabismus,  and  hence  the  precise  measurements 
have  been  given  with  each  muscle.  It  is,  therefore,  very  possi- 
ble that  the  lower  part  of  a  muscle  may  be  left  undivided  in  the 
operation,  being  more  in  the  background  than  the  rest.  The 
tendon  of  the  internal  rectus  is  nearer  to  the  cornea  than  either 
of  the  others. 

Inferior  Oblique. —  This  muscle  arises  by  a  flat  tendon 
from  the  orbital  plate  of  the  maxilla  on  the  outer  side  of  the 
lachrymal  groove.  It  runs  outwards  and  backwards  between 
the  orbit  and  the  inferior  rectus,  then  curves  upwards  between 
the  globe  and  the  external  rectus,  and  is  inserted  by  a  broad, 
thin  tendon  into  the  outer  and  back  part  of  the  eyeball  17.3 
mm.  from  the  corneo-scleral  junction,  or  livibiis. 

Action.  —  It  controls  the  upper  half  of  the  field  of  fixation, 
turns  the  eye  laterally  malarward,  increasing  in  abduction,  de- 
creasing in  adduction  ;  turns  the  eye  (vertically)  upwards,  in- 
creasing in  adduction,  diminishing  in  abduction.  (Hansell  and 
Reber.) 

The  tensor  tarsi  muscle  has  been  described  in  the  dissection 
of  the  face  (p.  49). 

Orbital  Branch  of  the  Maxillary  Nerve.  —  This  is  always  very  small,  and  is 
sometimes  absent.  It  comes  from  the  trunk  of  the  maxillary  in  the  spheno- 
maxillary fossa,  enters  the  orbit  through  the  sphenomaxillary  fissure,  and  divides 
into  two  branches.  Of  these,  one,  the  temporal,  lies  in  a  groove  in  the  outer  wall 
of  the  orbit,  and  after  sending  a  small  branch  to  the  lachrymal  nerve  in  the  orbit, 
passes  through  a  foramen  in  the  malar  bone  to  the  temporal  fossa.  It  then  pierces 
the  temporal  aponeurosis  an  inch  (.?.c  c.  m.)  above  the  zygoma,  and  supplies  the 
skin  of  the  temple  communicating  with  the  facial,  and  joining  frequently  with  the 
auriculo-temporal  branch  of  the  mandibular  n.  The  other  branch,  the  malar,  passes 
along  the  outer  part  of  the  floor  of  the  orbit,  imbedded  in  fat,  and  makes  its  exit 
through  a  foramen  in  the  malar  bone,  to  supply  the  skin  of  the  cheek  over  the 
malar  bone  (p.  63). 


78  DISSECTION    OF    THE    NECK. 


DISSECTION    OF   THE    NECK. 

Surface  Marking.  —  Before  the  student  reflects  the  skm  of 
the  neck  he  should  examine  the  skin  surface,  which  in  some 
places  is  raised,  in  others  depressed,  indicating  thereby  uneven- 
ness  of  the  subjacent  structures.  The  neck  is  bounded  above 
by  a  well-marked  transverse  ridge,  indicating  the  lower  border  of 
the  mandible,  and  at  its  lower  part  the  neck  is  bounded  by 
another  ridge  which  corresponds  with  the  clavicle.  Crossing 
obliquely  from  the  centre  of  the  neck  below  to  the  mastoid  pro- 
cess above  is  the  rounded  prominence  caused  by  the  sterno- 
mastoid,  and  crossing  this  muscle  diagonally  from  its  anterior  to 
its  posterior  border  is  the  external  jugular  vein,  which  varies  in 
size  in  different  subjects.  In  front  and  behind  the  sterno- 
mastoid  are  two  triangular  depressions ;  the  posterior  one,  it 
will  be  seen,  has  its  base  at  the  clavicle,  the  anterior  one  at  the 
mandible.  The  posterior  triangle  has  the  trapezius  as  its  outer 
boundary,  but  this  border  is  only  well  defined  inferiorly,  where 
the  hollow  becomes  most  marked,  and  takes  the  name  of  the 
supra-clavicular  or  Mohrenheim's  fossa.  In  this  is  placed  deeply 
the  subclavian  artery,  the  posterior  belly  of  the  omo-hyoid,  and 
the  brachial  plexus.  In  front  of  the  sterno-mastoid  is  another 
triangular  hollow  space  with  its  base  upwards ;  this  is  called  the 
carotid  triangle,  for  in  it  lies  the  carotid  artery  immediately  be- 
neath the  anterior  border  of  the  sterno-mastoid.  The  body 
of  the  hyoid  bone  can  always  be  felt  in  the  middle  line  below 
the  symphysis  of  the  mandible.  About  a  finger's  breadth 
below  the  hyoid  is  the  prominent  pomum  Adami  of  the  thyroid 
cartilage,  and  a  short  distance  below  this  cartilage  is  the  cricoid, 
separated  from  the  cartilage  above  by  the  crico-thyroid  mem- 
brane. The  cricoid  cartilage  corresponds  with  the  fifth  cervical 
vertebra,  and  from  it  the  trachea  passes  down,  gradually  reced- 
ing from  the  surface,  so  that  there  is,  especially  in  emaciated 
subjects,  a  deep  hollow  —  fonticulus  gutturis — immediately 
above  the  sternum.  In  front  of  the  second,  third,  and  fourth 
rings  of  the  trachea  is  the  isthmus  of  the  thyroid  gland,  and 
there  are  usually  another  four  rings  below  these  above  the 
sternum,  covered  more  or  less  l)y  the  depressor  muscles  of  the 
OS  hyoidcs. 

Dissection.  —  The   head   must    be   slightly  raised,   and    the 
face  turned  from  the  side  on  which  the  dissection  is  to  be  made. 


PLATYSMA    MYOIDES.  79 

Then  make  a  vertical  incision  through  the  skin,  clown  the  middle 
of  the  neck  from  the  symphysis  of  the  mandible  to  the  sternum  ; 
a  second  along  the  clavicle  to  the  acromion  ;  a  third  along  the 
base  of  the  mandible  as  far  as  the  mastoid  process.  Reflect  the 
skin  and  subcutaneous  fat,  and  expose  the  cutaneous  muscle, 
called  the  platysma  myoides.  Between  the  platysma  and  the 
skin  is  a  layer  of  adipose  tissue,  called  the  snpci^cial  fascia.  It 
varies  in  thickness  in  different  subjects,  but  is  generally  more 
abundant  at  the  upper  part  of  the  neck,  especially  in  corpulent 
individuals,  in  whom  it  occasions  a  double  chin. 

Platysma  Myoides. — The  platysma  myoides  is  the  thin 
cutaneous  muscle  covering  the  front  and  side  of  the  neck.  It 
arises  from  the  subcutaneous  tissue  over  the  pectoralis  major, 
trapezius,  and  deltoid  muscles  ;  thence  proceeding  obliquely  over 
the  clavicle  and  the  side  of  the  neck,  its  fibres  become  more 
closely  aggregated,  and  terminate  thus :  The  anterior  cross 
those  of  the  opposite  platysma,  immediately  below  the  symphy- 
sis of  the  mandible,  and  are  lost  in  the  skin  of  the  chin  ;  the 
middle  are  attached  along  the  base  of  the  mandible ;  the  pos- 
terior cross  the  masseter  muscle,  and  terminate,  partly  in  the 
subcutaneous  tissue  of  the  cheek,  partly  in  the  muscles  at  the 
corner  of  the  mouth  blending  with  the  depressor  anguli  oris 
and  orbicularis.* 

The  platysma  forms  a  strong  muscular  defence  for  the  neck. 
It  is  also  a  muscle  of  expression. •)•  It  is  supplied  with  nerves 
by  the  cervical  plexus,  and  by  the  cervical  branch  of  the  facial 
nerve. 

Dissection.  —  Cut  through  the  platysma  near  the  clavicle 

*  Some  of  the  uppermost  fibres  of  this  part  of  the  platysma  take  the  name  of 
mtiscidits  risoriics :  this  has  been  described  among  the  muscles  of  the  face. 

t  If  the  entire  muscle  be  pennanently  contracted  it  may  occasion  wry-neck, 
though  distortion  from  such  a  caxise  is  an  exceedingly  rare  occurrence.  A  case  in 
point  is  related  by  Mr.  Gooch  {Chinirg.  Wbr^s),  in  which  a  complete  cure  was 
effected,  after  the  failure  of  all  ordinary  means  of  relief,  by  the  division  of  the 
platysma  a  little  below  the  mandible. 

The  platysma  myoides  belongs  to  a  class  of  muscles  called  cutaneous ;  from 
their  office  of  moving  the  skin.  There  are  not  many  in  man,  e.xcept  upon  the 
neck  and  face,  and  there  is  a  little  one  (pahnaris  brevis)  in  the  the  palm  of  the  hand. 
To  understand  their  use  thoroughly  we  must  refer  to  the  lower  orders  of  animals, 
in  whom  they  fulfil  very  important  functions,  by  moving  not  only  the  skin,  but 
also  its  appendages.  For  instance,  by  muscles  of  this  kind  the  hedgehog,  porcu- 
pine, and  animals  of  that  family  can  roll  themselves  up  and  erect  their  quills;  we 
are  all  familiar  with  the  broad  '' paiuiiculus  caruosus  "  on  the  sides  of  herbivorous 
quadrupeds,  which  enables  them  to  twitch  their  skins,  and  thus  rid  themselves  of 
insects.  In  birds,  too,  these  cutaneous  muscles  are  extremely  numerous,  each 
feather  having  appropriate  muscles  to  moye  it, 


8o 


EXTERNAL  JUGULAR  VEIN. 


and  turn  it  upwards.  Beneath  it  lies  the  general  investment  of 
the  neck,  called  the  deep  cervical  fascia.  Upon  this  fascia  we 
trace  the  superficial  branches  of  the  cervical  plexus  of  nerves, 
the  external  jugular  vein,  and  a  smaller  vein  in  front,  called  the 
anterior  jugular.  These  superficial  veins  are  so  variable  in  size 
and  course  that  a  general  description  only  is  applicable. 

External  Jugular  Vein.  —  The  external  jugular  vein  is 
formed  within  the  substance  of  the  parotid  gland  by  the  junction 
of  the  temporal  and  internal  maxillary  veins.  After  receiving 
the  transverse  facial  and  posterior  auricular  veins,  it  appears  at 
the  lower  border  of  the  gland,  crosses  obliquely  over  the  sterno- 


Small  occipital  n. 

_ Auricularismagnus 

.  ^<j.    Nervus      accpssor- 

V     ,\   Descending  branch 

'  1  '  "^  of  cervical  plexus. 


Superficial  cervical     / 
nerve.  i' 

External  jugular  v. 

Anterior  jugular  v.  '^  ^     Ji 

Cervical  branch  of   \     Im  iLM 

facial  n.  '\  /|f  JJP'I 


Fig.  32.  — Diagram  of  the  Superficial  Nerves  and  Veins  of  the  Neck. 


mastoid  muscle  (Fig.  32),  running  along  its  posterior  border, 
nearly  as  low  down  as  the  clavicle,  where  it  pierces  the  deep 
cervical  fascia  and  terminates  in  the  subclavian  vein.  Accom- 
panying the  vein  in  its  upper  part  is  the  auricularis  magnus 
nerve,  and  cros.sing  it,  about  the  middle,  is  the  superficial  cervi- 
cal nerve,  both  being  branches  of  the  superficial  cervical  plexus. 
It  is  usually  provided  with  two  pairs  of  valves  —  the  lower,  im- 
perfect, close  to  its  termination  in  the  subclavian  vein  ;  the  up- 
per, placed  about  an  inch  and  a  half  (3.8  cm.)  above  the  clavicle. 
A  line  drawn  from  the  angle  of  the  mandible  to  the  middle 
of  the  clavicle  would  indicate  its  course.  To  trace  the  vein, 
during  life,  press  upon  it  just  above  the  clavicle  ;  but  do  not  be 


CUTANEOUS    NERVES    OF    THE    NECK.  8 1 

surprised  if  you  fail  to  find  it  ;  it  is  sometimes  wanting,  and 
frequently  very  small. 

Near  the  angle  of  the  mandible  the  external  jugular  vein 
communicates  by  a  large  branch  with  the  internal  jugular,  and 
about  its  middle  it  is  joined  by  a  large  vein  — posterior  external 
jugular — from  the  occipital  region. 

Before  its  termination  the  external  jugular  vein  generally  re- 
ceives the  supra-scapular,  posterior  scapular,  and  other  unnamed 
veins  :  a  disposition  very  embarrassing  to  the  surgeon,  because 
there  is  a  confluence  of  veins  immediately  over  the  subclavian 
artery  in  the  place  where  it  is  usually  tied. 

Anterior  Jugular  Vein.  — The  anterior  jugular  vein  is  situ- 
ated more  in  the  middle  of  the  neck,  and  is  much  smaller  than 
the  external  jugular.  It  commences  by  small  branches  below 
the  chin,  and  runs  down  the  front  of  the  neck,  nearly  to  the 
sternum  ;  it  then  curves  outwards,  beneath  the  sterno-mastoid 
muscle,  and  opens  either  into  the  external  jugular  or  the  sub- 
clavian vein.  We  commonly  meet  with  two  anterior  jugular 
veins,  one  on  either  side ;  immediately  above  the  sternum  they 
communicate  by  a  transverse  branch. 

The  size  of  the  anterior  jugular  vein  is  inversely  proportionate 
to  that  of  the  external  jugular.  When  the  external  jugular  is 
small,  or  terminates  in  the  internal  jugular,  then  the  anterior 
jugular  becomes  an  important  supplemental  vein,  and  attains 
considerable  size.  It  is  not  uncommon  to  find  it  a  quarter  of 
an  inch  (6  mm.)  in  diameter,  and  we  have  seen  it  nearly  half  an 
inch  (12.5  mm.).  These  varieties  should  be  remembered  in 
tracheotomy. 

Superficial  lymphatic  glands  are  sometimes  found  near  the 
cutaneous  veins  of  the  neck.  From  four  to  six  in  number,  they 
are  small  and  escape  observation  unless  enlarged  by  disease. 
One  or  two  are  situated  over  the  sterno-mastoid  muscle  ;  others, 
near  the  mesial  line. 

Cutaneous  Nerves  of  the  Neck.  —  The  cutaneous  nerves 
of  the  neck  are  the  superficial  branches  of  the  cervical  plexus  ; 
the  plexus  itself  cannot  at  present  be  seen.  It  is  formed  by 
the  communications  of  the  anterior  divisions  of  the  four  upper 
cervical  nerves,  and  lies  under  the  sterno-mastoid  muscle,  close 
to  the  transverse  processes  of  the  four  upper  cervical  vertebrse, 
resting  on  the  levator  anguli  scapulae  and  the  scalenus  medius. 
The  superficial  branches  of  the  plexus  emerge  from  beneath  the 
posterior  border  of  the  sterno-mastoid,  and  take  different  direc- 
tions.    They  are  named  thus  (Fig.  32)  :  — 


82         CERVICAL  BRANCH  OF  THE  FACIAL  NERVE. 


Superficial  branches  of 
the  cervical  plexus. 


Ascending  branches     .         .         .     i  Great  auricular. 
°  (  Small  occipital. 

Transverse  branch        .         .         .       Superficial  cervical. 

(  Sternal. 
Descending  branches  .         .         .    <  Clavicular. 

f  Acromial. 


The  ^^eaf  auricular  n.  comes  from  the  second  and  third  cervical  nerves,  winds 
round  the  posterior  border  of  the  sterno-mastoid,  and  ascends  obliquely  over  that 
muscle,  near  the  external  jugular  vein,  towards  the  parotid  gland.  Near  the  gland 
it  divides  into  two  principal  branches,  of  which  the  anterior  or  facial  branches 
are  distributed  to  the  skin  over  the  parotid  gland,  where  they  join  branches  from 
the  facial  nerve,  and  to  the  side  of  the  cheek ;  the  posterior  or  am-iciilar,  after 
ascending  a  short  distance,  give  off  a  branch,  which  ramifies  mainly  upon  the 
cranial  aspect  of  the  cartilage  of  the  ear ;  and  a  smaller  branch,  the  mastoid,  which 
supplies  the  skin  over  the  mastoid  process.  Other  filaments  of  this  nerve  com- 
municate in  the  substance  of  the  parotid  gland  with  branches  of  the  facial  nerve. 

The  small  occipital  ti.  comes  from  the  second  cervical  nerve,  and  is  occasionally 
double.  It  ascends  along  the  posterior  border  of  the  sterno-mastoid  muscle  to  the 
occiput,  where  it  supplies  the  back  of  the  scalp,  and  communicates  \rith  the  great 
occipital,  the  great  auricular,  and  the  posterior  auricular  nerves.  It  also  sends  off 
one  branch,  which  is  distributed  to  the  skin  of  the  temporal  region,  and  another 
aitriciUar  to  the  pinna  of  the  ear.  Beneath  the  sterno-mastoid  this  nerve  com- 
monly forms  a  loop,  which  embraces  the  nervus  accessorius,  and  sends  a  branch 
to  it. 

The  superficial  cervical  n.  comes  from  the  second  and  third  cervical  nerves.  It 
passes  transversely  fonvards  over  the  sterno-mastoid  muscle,  and  supplies  the  front 
of  the  neck.  Some  of  its  filaments  ascend  towards  the  mandible,  and  join  the 
cer\-ical  branch  of  the  facial  nerve ;  other  filaments  descend  and  supply  the  skin 
in  front  of  the  neck  as  low  as  the  sternum. 

The  descending  or  supra-clavicular  branches  are  derived  from  the  third  and 
fourth  cervical  nerves,  and  divide  into  three  branches,  which  cross  over  the 
clavicle,  and  supply  the  skin  of  the  front  of  the  chest  and  shoulder.  Of  these, 
one,  called  the  internal  or  sternal,  supplies  the  skin  over  the  sternal  end  of  the 
clavicle  and  the  upper  part  of  the  sternum ;  another,  the  middle  or  clavicular, 
passes  over  the  middle  of  the  clavicle,  and  is  distributed  to  the  skin  over  the 
pectoral  muscle,  the  mammary  gland,  and  the  nipple ;  the  third,  named  exterttal 
or  acromial,  crosses  over  the  trapezius  and  acromion  to  supply  the  skin  of  the 
shoulder. 

Reviewing  these  cutaneous  branches  of  the  cervical  plexus, 
we  find  that  they  have  a  very  wide  distribution,  for  they  supply 
the  skin  covering  the  following  parts  —  viz.,  the  ear,  the  back 
of  the  scalp,  the  side  of  the  cheek,  the  parotid  gland,  the  front 
and  side  of  the  neck,  the  upper  and  front  part  of  the  chest  and 
shoulder. 

Cervical  Branch  of  the  Facial  Nerve.  —  Look  for  this 
branch  beneath  the  fascia  near  the  angle  of  the  mandible  (p.  80). 
It  leaves  the  parotid  gland,  and,  piercing  the  deep  cervical  fascia, 
divides  into  filaments  which  curve  forwards  below  the  mandible  ; 
.some  of  these,  forming  arches,  join  the  superficial  cervical 
branch  of  the  cervical  plexus ;  others  supply  the  platysma  and 
skin. 


DEEP    CERVICAL    FASCIA. 


83 


Deep  Cervical  Fascia.  —  Now  turn  your  attention  to  the 
membranous  investment  called  the  deep  cervical  fascia,  which 
encloses  the  several  structures  of  the  neck.     In  some  subjects 


thochlcam 


mFHATROCHLlAlt 


-■%--w..X/V'^^\\x>^^^^'«^""'^ 


Fig.  33- 


the  fascia  is  very  thin  ;  in  others,  with  strong  muscles,  it  is 
proportionally  dense  and  resisting.  It  is  always  stronger  in 
particular  situations,  for  the  more  effective  protection  of  the 
parts  beneath  ;  for  instance,  in  front  of  the  trachea,  in  the  fossa 


84  DEEP    CERVICAL    FASCIA. 

above  the  clavicle,  and  below  the  angle  of  the  mandible.  It  not 
only  covers  the  soft  parts  of  the  neck  collectively,  but,  by  its 
inflections,  forms  separate  sheaths  for  the  muscles,  vessels,  and 
glands.  It  isolates  them,  and  keeps  them  in  their  proper  rela- 
tive position.  A  lengthened  description  of  its  numerous  layers 
would  be  not  only  extremely  tedious,  but  unintelligible,  without 
considerable  knowledge  of  the  anatomy  of  the  neck.  We  pro- 
pose, therefore,  to  give  only  a  general  outline  of  the  fascia,  and 
of  its  principal  layers,  commencing  from  behind. 

Tracing  it  from  behind,  we  find  that  the  cervical  fascia  (some- 
times called  deep  cervical  or  viiisctilar  fascia  of  the  neck)  is 
attached  to  the  ligamentum  nuchas  and  to  the  spinous  and 
transverse  processes  of  the  cervical  vertebras.  From  these 
attachments  it  passes  forwards  over  the  posterior  triangle  of 
the  neck  to  the  posterior  border  of  the  sterno-mastoid,  where  it 
splits  into  two  layers,  superficial  and  deep,  which  invest  that 
muscle  and  reunite  at  its  anterior  border.  The  superficial  layer 
passes  towards  the  mesial  line,  where  it  becomes  continuous 
with  the  corresponding  fascia  of  the  opposite  side.  The  layer 
which  Hes  in  front  of  the  sterno-mastoid  is  attached  above  to 
the  base  of  the  mandible,  and  passes  over  the  parotid  gland 
to  the  zygoma,  to  the  mastoid  process,  and  the  superior  curved 
line  of  the  occipital  bone.  Traced  downwards,  we  find  it  at- 
tached to  the  clavicle  and  to  the  upper  border  of  the  ster- 
num. In  the  middle  line  it  is  closely  connected  to  the  hyoid 
bone,  and  below  the  thyroid  body  divides  into  two  layers,  one 
being  attached  to  the  front  of  the  upper  border  of  the  sternum, 
the  other  to  the  back  of  the  upper  border  of  the  same  bone. 
Between  these  layers  there  is  a  well-marked  interval,  contain- 
ing more  or  less  fat,  and  one  or  two  small  lymphatic  glands. 
This  layer  forms  investing  sheaths  for  the  depressor  muscles  of 
the  OS  hyoides  and  larynx. 

The  deep  layer  —  viz.,  that  which  passes  beneath  the  sterno- 
mastoid  —  forms  the  common  sheath  for  the  carotid  artery,  in- 
ternal jugular  vein,  and  the  pneumogastric  nerve,  which  lie 
behind  this  muscle ;  the  structures  contained  in  the  carotid 
sheath  are  separated  from  each  other  by  delicate  septa.  The 
fascia  is  continued  behind  the  pharynx  (constituting  the  prcE- 
vertcbral  fascia)  to  join  the  fascia  of  the  opposite  side,  while 
another  prolongation  passes  in  front  of  the  trachea  beneath  the 
sterno-thyroid  muscle.  Below,  it  is  attached  to  the  first  rib,  to 
which  it  binds  down  the  intermediate  tendon  of  the  omohyoid  ; 


DEEP    CERVICAL    FASCIA.  8$ 

and  still  further  clown  it  is  continuous  in  the  chest  with  the 
pericardium.  It  may  also  be  traced  under  the  clavicle  along  the 
a.xillary  vessels  and  nerves  into  the  axilla.  Above,  it  is  attached 
to  the  angle  of  the  mandible,  from  which  it  extends  backwards 
to  the  styloid  process,  and  forms  the  stylo-matidibnlar  ligament. 
Thence  it  is  attached  to  the  base  of  the  skull,  the  petrous  por- 
tion of  the  temporal  bone,  and  the  basilar  process  of  the  occip- 
ital bone. 

A  correct  knowledge  of  the  attachments  of  the  principal  layers 
of  the  cervical  fascia  is  essential  to  a  right  understanding  of  the 
course  which  pus  takes  when  it  forms  in  the  neck.  For  in- 
stance, suppose  the  pus  to  be  formed  at  the  lower  part  of  the 
neck.  If  it  be  seated  under  the  superficial  layer  (which  is  at- 
tached to  the  clavicle),  it  may  burrow  beneath  the  clavicle  into 
the  axilla.  But  if  it  be  seated  beneath  the  deep  layer  (which  is 
attached  to  the  first  rib),  then  it  becomes  more  serious,  since 
the  pus  may  travel  through  the  loose  tissue  by  the  side  of  the 
pharynx,  and  make  its  way  into  the  chest,  where  it  may  burrow 
down  the  anterior  or  the  posterior  mediastinum,  and  burst  into 
the  trachea  or  the  oesophagus. 

Besides  forming  sheaths  for  the  several  structures  of  the  neck, 
there  are  other  purposes  to  which  the  cervical  fascia  is  subser- 
vient. The  firm  attachment  of  its  layers  to  the  sternum,  the 
first  rib,  and  the  clavicle,  forms  a  fibrous  barrier  at  the  upper 
opening  of  the  chest,  which  supports  the  soft  parts,  and  prevents 
their  yielding  to  the  pressure  of  the  atmosphere  during  inspira- 
tion. Dr.  Allan  Burns  *  first  pointed  out  this  important  func- 
tion of  the  cervical  fascia,  and  has  recorded  a  case  exemplifying 
the  results  of  its  destruction  by  disease. 

Moreover,  the  great  veins  at  the  root  of  the  neck,  namely,  the 
internal  jugular,  subclavian,  and  innominate,  are  so  closely  united 
by  the  cervical  fascia  to  the  adjacent  bones  and  muscles,  that 
when  divided  they  gape.  They  are,  as  the  French  express  it, 
"  canaiis^es,"  and  are  therefore  better  able  to  resist  the  pressure 
of  the  atmosphere,  which  tends  to  render  them  flaccid  and  im- 
pervious during  inspiration.  But  this  anatomical  disposition  of 
the  great  veins  makes  them  more  liable  to  the  entrance  of  air 
when  wounded.  Instances  of  death  have  been  recorded,  result- 
ing from  the  sudden  entrance  of  air  into  the  veins  during  opera- 
tions about  the  neck,  or  even  the  axilla. 

*  "  Surgical  Anatomy  of  the  Head  and  Neck." 


86 


STERNO-CLEIDO-MASTOIDEUS. 


Sterno-cleido-mastoideus.  -^Thc  sterno-cleido-mastoideus 
is  the  large  muscle  which  passes  obliquely  across  the  neck.  It 
arises  by  a  rounded  tendon  from  the  upper  part  of  the  sternum, 
and  by  fleshy  fibres  from  the  sternal  third  of  the  clavicle.  It 
is  inserted  by  a  thick  tendon  into  the  external  surface  of  the 
mastoid  process,  and  by  a  thin  aponeurosis  into  about  the  outer 
half  of  the  superior  curved  ridge  of  the  occipital  bone. 


Fig  34.  —  Sterno-cleido-mastoid  M.  and  Muscles  Above  and  Below  the  Hyoid  Bone. 

.  Anterior  belly  of  the  digastric  on  the  left  side.  2.  Posterior  belly  of  the  digastric.  3.  Tendon  of 
the  digastric  and  pulley  through  which  it  passes.  4.  .Stylo-hyoid  pierced  by  the  posterior  belly 
of  the  digastric.  5.  Mylo-hyoid  in.  6.  Hyo-glossus  in.,  the  anterior  part  being  covered  by 
the  preceding  muscle.  7.  Sterno-cleido-niastoid  m.  8.  Sternal  portion  of  the  sterno-mastoid 
m.  q.  Clavicular  portion  of  the  sterno-mastoid  m.  10.  Sterno-hyoici  m.  of  the  left  side. 
II.  Sterno-hyoid  m.  of  the  right  side.  12,  12.  Anterior  and  posterior  bellies  of  the  omo- 
hyoid ni.  13.  'Ihyro-hyoid  m.  14,  14  Sterno-thyroid  m.  15.  Anterior  part  of  the  inferior 
constrictor  m.  of  the  pharynx.  16.  Occipito-frontalis  m.  17,  17.  The  two  fasciculi  of  the 
retrahens  aurem.  18.  Trapezius  m.  19.  Capitis  portion  of  the  splenius  capitis  et  colli  m. 
20.  Colli  portion  of  the  same  m.  21.  Levator  anguli  scapul.T.  22.  Scalenus  posticus  m. 
27,.  Scalenus  amicus  m.  24.  Superior  part  of  the  deltoid  m.  25.  Clavicular  portion  of  the 
pectoralis  major  m.  26.  Anterior  and  infc  ior  part  of  the  platysnia-myoid  m.  27.  Depressor 
anguli  oris  in.  28.  Transverse  portion  of  the  preceding  m.,  blending  with,  although  external 
to,  the  depressor  labii  inferioris  m      29.    Masseter  m.     30.    Buccinator  m. 


The  Sternal  origin  of  the  muscle  is  at  first  separated  from  the 
clavicular  by  a  slight  interval  ;  subsequently  the  sternal  fibres 
gradually  overlap  the  clavicular.  The  muscle  is  confined  by  its 
strong  sheath  of  fascia,  in  such  a  manner  that  it  forms  a  slight 


TRIANGLES    OF   THE    NECK.  8/ 

curve,  with  the  convexity  forwards.  Observe  especially  that  its 
front  border  overlaps  the  common  carotid  artery ;  along  this 
border  we  make  the  incision  in  the  operation  of  tying  the  vessel. 
Action  of  Sterno-mastoid. — When  both  sterno-mastoids 
act  simultaneously  they  draw  the  head  and  neck  forwards  and 
downwards  (the  occiput  being  slightly  depressed),  and  are  there- 
fore especially  concerned  in  raising  the  head  from  the  recumbent 
position.  When  one  sterno-mastoid  acts  singly,  it  turns  the 
head  obliquely  towards  the  opposite  shoulder  (elevating  the 
chin) ;  in  this  action  it  co-operates  with  the  splenius  of  the  other 
side.*  On  emergency,  the  sterno-mastoid  acts  as  a  muscle  of 
inspiration,  by  raising  the  sternum  ;  its  fixed  point  being,  in  this 
case,  at  the  head. 

The  sterno-mastoid  is  supplied  by  three  nutrient  arteries  —  an  upper,  a  middle, 
and  a  lower.  The  upper  sterno-mastoid  artery,  a  branch  of  the  occipital,  enters 
the  muscle  with  the  n.  accesorius  [spinal  accessory)  close  to  the  mastoid  process  of 
the  temporal  bone;  the  middle  mastoid  is  a  branch  of  the  superior  thyroid,  and 
enters  the  under  surface  of  the  muscle,  crossing  over  the  common  carotid  on  a 
level  with  the  thyroid  cartilage ;  the  lower  mastoid  is  a  branch  of  the  supra-scap- 
ular, and  supplies  the  clavicular  portion  of  the  muscle,  close  to  its  origin. 

The  sterno-mastoid  is  supplied  with  nerves  by  the  n.  accessorius  [spinal  acces- 
sory), and  by  branches  from  the  deep  cervical  ple.xus ;  these  branches  come  from 
the  second  and  sometimes  the  third  cervical  nerves. 

Triangles  of  the  Neck.  —  Anatomists  avail  themselves  of 
the  oblique  direction  of  the  sterno-mastoid  muscle  to  divide  the 
neck  on  each  side  into  two  great  triangles,  an  anterior  and  a 
posterior  (Fig.  35).  The  base  of  the  anterior  triangle  is  formed 
by  the  mandible,  its  sides  by  the  mesial  line  and  the  front 
border  of  the  sterno-mastoid.  The  posterior  has  the  clavicle 
for  the  base,  while  the  sides  are  defined  by  the  hind  border  of 
the  sterno-mastoid  and  the  front  border  of  the  trapezius. 

The  omo-hyoid  muscle,  which  crosses  the  neck  under  the 
sterno-mastoid,  subdivides  these  primary  triangles  into  four 
smaller  ones  (Fig.  3  5)  of  unequal  size  :  an  anterior  superior,  an 
anterior  inferior,  a  posterior  superior,  and  a  posterior  inferior. 
The  direction  of  the  omo-hyoid  muscle  renders  their  boundaries 
at  once  obvious. 

Contents  of  Posterior  Triangle. — The  fat  and  connective 

*  The  single  action  of  the  muscle  is  well  seen  when  it  becomes  rigid  and  causes 
a  wry-neck.  Other  means  of  relief  failing,  the  division  of  the  muscle  near  its 
origin  is  sometimes  beneficial  in  curing  the  distortion.  In  deciding  as  to  the  pro- 
priety of  this  operation,  we  should  be  careful  to  e.xamine  the  condition  of  the 
other  muscles,  lest,  after  having  divided  the  sterno-mastoid,  we  should  be  disap- 
pointed in  removing  the  deformity. 


88 


CONTENTS  OF  POSTERIOR  TRIANGLE. 


tissue  must  now  be  carefully  removed  from  the  posterior  tri- 
angle. The  following  muscles  will  be  seen  forming  its  floor  : 
viz.,  beginning  from  above,  the  splenius  capitis,  the  levator  an- 
guli  scapulae,  the  scalenus  medius  and  posticus,  and  a  small 
portion  of  the  serratus  magnus.  The  posterior  belly  of  the 
omo-hyoid  crosses  this  triangle  about  an  inch  (2.^  c.  7n.)  above 
the  clavicle,  and  subdivides  it  into  two  unequal  parts  —  an  upper 
or  occipital,  and  a  lower  or  supra-clavicular*  In  the  occipital 
triangle,  the  larger  of  the  two,  besides  the  muscles  just  men- 
tioned (with  the  exception  of  the  serratus  magnus^,  are  found 


N.  accessorius. 

Digastricus. 
Os  hyoides. 

Omo-hyoideus. 


Sterno-mastoid  mus- 
cle drawn  aside. 

Splenius  capitis. 


Levator  anguli  scap- 
ula;. 


Scalenus  medius. 


Scalenus  anticus. 


Fig.  35.  —  Diagram  of  Triangi.es  of  thk  Neck. 

I.    Superior  carotid    triangle.      2.    Inferior   carotid   triangle.      3.    Occipital   triangle.      4.    Supra- 
clavicular triangle.     5.   Submandibular  triangle. 

the  descending  branches  of  the  cervical  plexus,  and  passing 
obliquely  downward  from  beneath  the  sterno-mastoid  is  the 
spinal  accessory  nerve,  which  enters  the  under  part  of  the  tra- 
pezius. Curving  round  the  posterior  border  of  the  sterno- 
mastoid,  and  becoming  superficial,  are  the  ascending  and 
transverse  branches  of  the  superficial  cervical  plexus.  The 
transversalis  colli  (posterior  scapular)  artery  and  vein,  and  its 
branch,  the  superficialis  colli  (which  chiefly  supplies  the  trape- 
zius), cross  transversely  outwards  the  lower  part  of  the  space. 
A  chain  of  lymphatic  glands  is  also  found  along  the  posterior 
border  of  the  sterno-mastoid. 


*  Mohrenhcim'.s  foss.x 


SUPRA-CLAVICULAR    TRIANGLE.  89 

Nervus  Accessorius. — The  upper  part  of  the  sterno-mastoid  is  traversed 
obliquely  by  a  large  nerve  called  the  spinal  accessory  or  n.  accessorius.  This 
nerve — the  eleventh  cranial  —  consists  of  two  parts;  one,  the  accessory,  arises 
from  the  side  of  the  medulla  below  the  pneumogastric  nerve;  the  other,  the 
spinal  part,  arises  from  the  cervical  portion  of  the  spinal  cord  by  a  series  of  fil- 
aments from  the  lateral  tract  as  low  down  as  the  sixth  cervical  vertebra.  The 
spinal  portion  ascends  between  the  ligamentum  denticulatum  and  the  posterior 
roots  of  the  spinal  nerves,  through  the  foramen  magnum  into  the  skull.  Within 
the  cranium  the  two  parts  unite  and  form  a  single  nerve,  which  leaves  the  skull 
through  the  foramen  jugulare.  Here  the  accessory  portion  is  connected  with  the 
ganglion  of  the  root  of  the  pneumogastric  by  several  filaments ;  and  lower  down  it 
again  joins  the  pneumogastric  at  the  ganglion  of  the  trunk,  below  which  the  two 
nerves  become  blended.  The  accessory  and  spinal  portions  communicate  in  the 
foramen  jugulare.  Below  the  foramen  the  spinal  part  runs  behind  the  internal 
jugular  vein,  the  digastric  and  stylo-hyoid  muscles,  and  then  pierces  obliquely  the 
upper  third  of  the  sterno-mastoid.  Emerging  beneath  its  outer  border,  it  crosses 
the  posterior  triangle  of  the  neck  to  the  under  surface  of  the  trapezius,  to  which  it 
is  distributed.  The  nervus  accessorius  supplies  also  the  sterno-ma.stoid  in  its 
passage  through  it,  and  here  it  joins  some  branches  from  the  third  cervical.  After 
leaving  the  muscle  it  is  joined  by  branches  from  the  second  and  third  cervical 
nerves.  Beneath  the  trapezius  it  forms  a  plexus  with  the  third  and  fourth  cervical 
nerves.  The  upper  mastoid  artery,  a  branch  of  the  occipital,  enters  the  sterno- 
mastoid  with  the  nerve. 

Supra-Clavicular  Triangle.* — The  supra-clavicular  ov sub- 
clavian  triangle  is  bounded  below  by  the  clavicle,  in  front  by 
the  outer  border  of  the  sterno-mastoid,  and  above  by  the  poste- 
rior belly  of  the  omo-hyoid  muscle.  The  area  of  the  triangle 
thus  formed  will  vary  in  proportion  to  the  obliquity  of  the  omo- 
hyoid muscle,  and  the  extent  to  which  the  sterno-mastoid  and 
trapezius  are  attached  to  the  clavicle.  The  depth  of  the  vessels 
and  nerves  contained  in  this  space  depends  not  only  upon  the 
degree  to  which  the  clavicle  arches  forwards,  but  varies  with 
the  elevation  and  depression  of  the  shoulder. 

Dissection.  —  The  descending  branches  of  the  cervical  plexus, 
together  with  some  fat,  should  now  be  cut  through  and  turned 
aside,  when  a  layer  of  a  fascia  which  binds  down  the  omo-hyoid 
muscle  to  the  clavicle  will  be  exposed.  Beneath  this  is  a  deeper 
layer  of  fascia,  which  covers  the  subclavian  vessels  and  brachial 
plexus  of  nerves,  and  descends  with  them  under  the  clavicle 
into  the  axilla.  Between  these  two  layers  we  meet  with  more 
or  less  fat  and  connective  tissue  and  lymphatic  glands  continu- 
ous with  those  in  the  axilla.  It  will  be  easily  understood  how  a 
collection  of  pus  in  the  axilla  may  ascend  in  front  of  the  vessels 
and  point  above  the  clavicle,  or,  vice  versd,  how  pus  formed 
in  the  neck  may  travel  under  the  clavicle  and  point  in  the  axilla. 

Near  the  posterior  border  of  the  sterno-mastoid  muscle  the 
external   iugular  vein   passes  through  both  layers  of  the  deep 

*  Mohrenheim's  fossa. 


QO  DISSECTION    OF    THE    ANTERIOR   TRIANGLE. 

fascia  and  terminates  in  the  subclavian  ;  but  before  its  termina- 
tion it  is  commonly  joined  by  the  supra-scapular,  the  posterior 
scapular,  and  other  unnamed  veins  proceeding  from  the  sur- 
rounding muscles  ;  so  that  there  is  in  this  situation  a  confliience 
of  veins,  which,  when  large  or  distended,  is  exceedingly  embar- 
rassing. 

The  fascia  and  the  glands  should  be  removed,  and  the  follow- 
ing objects  carefully  dissected.  Behind  and  nearly  parallel  with 
the  clavicle  is  the  supra-scapular  (transversalis  humeri)  artery,  a 
branch  of  the  thyroid  axis.  A  little  higher  is  the  transversalis 
colli,  or  posterior  scapula  (commonly  a  branch  of  the  thyroid 
axis),  which  crosses  the  lower  part  of  the  neck  towards  the  pos- 
terior superior  angle  of  the  scapula.  Both  these  arteries  are 
very  irregular  in  respect  to  their  origin,  tJie  last  particularly 
being  often  given  off  from  the  subclavian  in  the  third  part  of  its 
course.  Search  for  the  outer  border  of  the  scalenus  anticus, 
which  descends  from  the  transverse  processes  of  the  cervical 
vertebrae  to  the  first  rib;  running  down  longitudinally  upon  it 
may  be  seen  the  phrenic  nerve.  The  subclavian  vein  lies  upon 
the  first  rib  in  front  of  the  insertion  of  the  anterior  scalene 
muscle  behind  the  clavicle,  so  that  it  is  not  usually  seen  in  this 
triangle.  The  subclavian  artery  rises  up  into  the  neck  as  high 
as  an  inch  {2.^  c.  m:)  above  the  clavicle,  and  sometimes  on  the 
right  side  as  high  as  an  inch  and  a  half  {^.8  c.  m.).  It  appears 
higher  than  the  vein,  emerging  beneath  the  outer  border  of  the 
scalenus  anticus,  and  care  must  be  taken  to  preserve  the  small 
branch  from  the  brachial  plexus,  which  crosses  the  artery  and 
proceeds  to  the  subclavius  muscle.  The  large  nerves  constitut- 
ing the  brachial  plexus  come  out  between  the  scalenus  anticus 
and  medius,  higher  than  the  subclavian  artery,  and  on  a  plane 
posterior  to  that  vessel.  These  different  objects  will  be 
described  in  detail  hereafter. 

Dissection  of  the  Anterior  Triangle.  - —  The  anterior  tri- 
angle must  now  be  dissected.  In  doing  so,  notice,  before  the 
deep  cervical  fascia  is  removed,  the  arching  forwards  of  the 
anterior  border  of  the  sterno-mastoid  muscle,  which  is  connected 
to  the  mandible  by  the  fascia,  so  that  the  common  carotid 
artery  is  concealed  from  view  before  the  parts  are  disturbed. 
The  anterior  triangle  is  bounded  behind  by  the  anterior  border 
of  the  stern o-ma.stoid,  in  front  by  the  middle  line  of  the  neck, 
and  above  by  the  lower  border  of  the  mandible.  Covering  the  tri- 
angle are  the  superficial  and  deep  cervical  fasciae  and  the  platys- 


STERNO-HYOID.  9 1 

ma;  passing  across  it  are  the  superficial  cervical  n.,  the  sub- 
mandibular branch  of  the  facial  nerve ;  and  descending  in  front 
is  the  anterior  jugular  vein.  This  space  is  subdivided  by  the 
anterior  belly  of  the  omo-hyoid  into  a  superior  and  an  inferior 
rc?ri?/^V/ triangle,  and  above  them  is  a  third  triangle  mapped  out 
by  the  converging  belHes  of  the  digastric  muscle  and  the  man- 
dible, and  is  called  the  submandibular  or  digastric  trangle  (Fig. 
35,  p.  88). 

The  inferior  carotid  tria^igle  is  bounded  above  and  below  by 
the  omo-hyoid  and  sterno-mastoid  muscles,  and  in  front  by  the 
middle  line.  The  muscles  forming  its  floor  are  the  sterno-hyoid 
and  sterno-thyroid  muscles,  and  lying  on  them  is  the  anterior 
jugular  vein  ;  in  the  middle  line  is  the  thyroid  body  covering  the 
trachea.* 

The  superior  carotid  triangle  has  for  its  boundaries  the  sterno- 
mastoid,  the  omo-hyoid,  and  the  posterior  belly  of  the  digastricus. 
Its  muscular  floor  is  formed  by  the  hyo-glossus,  the  middle  and 
inferior  pharyngeal  constrictors,  and  the  thyro-hyoid.  In  this 
space  are  found  the  bifurcation  of  the  common  carotid  into  its 
external  and  internal  divisions,  and  the  following  branches  of 
the  external  carotid  —  the  superior  thyroid,  lingual,  facial,  the 
occipital,  and  the  ascending  pharyngeal  arteries  —  their  accom- 
panying veins  and  the  internal  jugular  vein.  The  nerves  seen 
are  the  hypoglossal,  crossing  over  the  external  carotid,  the  sub- 
mandibular branch  of  the  facial,  the  spinal  accessory,  the  superior 
and  external  laryngeal  nerves,  and  in  front  of  the  carotid  sheath 
is  the  descendens  hypoglossi  n. 

The  digastric  triangle  will  be  described  subsequently  (p.  io6). 

Now  examine  the  flat  muscles  in  front  of  the  neck,  which  pull 
down  the  larynx  and  os  hyoides  —  namely,  the  sterno-hyoid, 
sterno-thyroid,  omo-hyoid,  and  thryo-hyoid.f  Remove  the  fascia 
which  covers  them,  disturbing  them  as  little  as  possible,  and 
take  care  of  the  nerves  (branches  of  the  descendens  hypoglossi), 
which  enter  their  outer  borders. 

Sterno-hyoid. — The  sterno-hyoid  arises  from  the  back  part 
of  the  sternum  and  posterior  sterno-clavicular  ligament,  from  the 
clavicle  and   occasionally  from  the  cartilage  of  the  first  rib,  and 

*  The  vessels  and  nerves  Ijring  within  and  upon  the  carotid  sheath  are  not  seen, 
as  they  are  situated  beneath  the  anterior  border  of  the  sterno-mastoid. 

t  The  sternohyoid  and  sterno-thyroid  muscles  often  present  shght  transverse 
tendinous  lines.  These  tendinous  intersections  are  quite  rudimentary  in  man ;  but 
in  some  animals  with  long  necks,  e.  _ir.,  the  giraffe,  they  are  so  developed  that  each 
dt-pressor  muscle  is  composed  of  alternrit'ons  of  muscle  and  tendon. 


92  STERNO-THVROID. 

is  inserted  into  the  lower  border  of  the  body  of  the  os  hyoides. 
It  is  supplied  by  the  first  three  cervical  nerves  through  the 
descendens  and  communicans  hypoglossi  entering  on  the  deep 
surface  near  the  upper  extremity.  Action  :  It  draws  down  the 
hyoid  bone  after  it  has  been  elevated  in  swallowing;  it  also 
fixes  the  hyoid  to  allow  the  sucking  motion  by  the  tongue. 
This  is  the  most  superficial  of  the  muscles  in  front  of  the 
neck.  We  cut  in  the  mesial  line  between  these  muscles  in 
tracheotomy. 

Sterno-thyroid. —  The  sterno-thyroid  arises  from  the  back 
part  of  the  sternum,  below  and  internal  to  the  origin  of  the 
sterno-hyoid,  and  the  cartilage  of  the  first  rib,  and  is  inserted 
into  the  oblique  ridge  on  the  ala  of  the  thyroid  cartilage.  Nerve 
supply  is  from  the  loop  of  the  descendens  and  communicans 
hypoglossi.  Action  is  similar  to  the  preceding  muscle.  This 
muscle  is  situated  immediately  under,  and  is  much  broader  than, 
the  sterno-hyoid. 

The  two  sterno-hyoid  muscles  converge  as  they  ascend  to 
their  insertions,  and  opposite  the  cricoid  cartilage  and  the  two 
or  three  upper  rings  of  the  trachea  they  are  in  contact  with  one 
another.  The  sterno-thyroid,  however,  diverge  to  their  inser- 
tions, but  are  in  contact  below,  the  result  of  which  is  that  the 
trachea  is  completely  covered  in  front  by  muscular  fibres. 

Omo-hyoid.  —  The  omo-hyoid  consists  of  two  fleshy  portions 
connected  by  a  tendon.  It  arises  from  the  upper  border  of  the 
scapula,  and  sometimes  from  the  ligament  over  the  notch,  and 
is  inserted  into  the  lower  border  of  the  body  of  the  os  hyoides 
just  external  to  the  sterno-hyoid.  From  the  scapula  it  comes 
nearly  horizontally  forwards  across  the  lower  part  of  the  neck, 
and  passes  beneath  the  sterno-mastoid,  over  the  sheath  of  the 
great  vessels  of  the  neck  on  a  level  with  the  cricoid  cartilage ; 
then,  changing  its  direction,  it  ascends  nearly  vertically  close  to 
the  outer  border  of  the  sterno-hyoid.  Thus  the  muscle  does  not 
proceed  straight  from  origin  to  insertion,  but  forms  an  obtuse 
angle  beneath  the  sterno-mastoid  muscle.  The  intermediate 
tendon  is  situated  at  the  angle  and  is  bound  down  to  the  first 
rib  and  the  sternum  by  a  process  of  the  deep  cervical  fascia. 
Action.  The  object  of  this  peculiar  direction  of  the  omo-hyoid 
appears  to  be  to  keep  tense  that  part  of  the  cervical  fascia 
which  covers  the  apex  of  the  pleura,  and  thus  to  resist  atmos- 
pheric pressure.  It  depresses  the  hyoid  bone  and  may  slightly 
elevate  the  scapula.      It  is  supplied  by  the  descendens  (from  the 


ACTION    OF    Till':    DIU'KKSSOK    MUSCL1':S.  93 

1 2th  n.)  and  communicans  hypoglossi  (from  the  2d  and  3d 
cervical  nn.).      Fig.  36,  p.  94. 

Relations  of  the  Omo-hyoid.  —  At  its  origin  the  omo- 
hyoid is  covered  by  the  trapezius,  then  by  the  clavicle  and  sub- 
clavius,  and  lastly,  by  the  sterno-mastoid  and  platysma  myoides. 
It  lies  on  the  scalenus  medius  and  anticus,  the  brachial  plexus, 
the  phrenic  nerve,  then  on  the  internal  jugular  vein,  pneumo- 
gastric  nerve  and  common  carotid  artery  enclosed  within  their 
common  sheath,  on  the  descendens  hypoglossi,  the  sterno- 
thyroid, and  thyro-hyoid  muscles. 

The  descendens  hypoglossi  sends  a  separate  branch  to  each 
belly  of  the  omo-hyoid.  These  depressors  are  supplied  with 
blood  by  the  superior  and  inferior  thyroid  arteries.  . 

Thyro-hyoid.  —  The  thyro-hyoid  arises  from  the  oblique 
line  on  the  ala  of  the  thyroid  cartilage,  and  runs  up  to  be 
inserted  into  the  lower  border  of  the  body  and  the  inner  half 
of  the  great  cornu  of  the  hyoid  bone.  This  muscle  is  a  con- 
tinuation of  the  sterno-thyroid.  It  is  supplied  by  a  special 
branch  of  the  hypoglossal  nerve  which  enters  the  muscle  close 
by  its  posterior  border,  in  company  with  the  hyoid  branch  of 
the  lingual  artery. 

Action.  —  It  elevates  the  thyroid  cartilage  in  swallowing ; 
is  associated  with  the  sterno-thyroid  in  depressing  the  hyoid 
bone.  In  front  of  the  muscle  are  the  omo-hyoid  and  sterno- 
hyoid muscles,  and  it  covers  the  thyro-hyoid  membrane,  the 
thyroid  cartilage,  and  the  superior  laryngeal  vessels  and  nerve 
as  they  enter  the  larynx. 

Action  of  the  Depressor  Muscles.  —  These  musics  depress 
the  larynx  in  the  utterance  of  low  notes.  That  the  larynx  is 
raised  or  depressed,  according  to  the  height  of  the  note,  may  be 
ascertained  by  placing  the  finger  on  it  while  singing  through 
an  octave.  The  omo-hyoid,  in  addition,  is  a  tensor  of  the  cervi- 
cal fascia,  and  draws  down  the  hyoid  bone  to  its  own  side.  The 
thyro-hyoid  depresses  the  hyoid  bone,  or  elevates  the  thyroid 
cartilage,  according  as  the  one  or  the  other  is  the  fixed  point. 

Dissection. — The  sterno-mastoid  muscle  must  now  be  cut 
transversely  through  the  middle,  and  the  two  ends  turned  up- 
wards and  downwards,  so  that  they  may  be  replaced  if  neces- 
sary. This  done,  notice  the  strong  layer  of  fascia  which  lies 
under  the  muscle  and  forms  part  of  its  sheath.  It  is  attached 
to  the  angle  of  the  mandible,  thence  descends  over  the  large 
vessels  of  the  neck,  and  is  firmly  connected  to  the  clavicle  and 


94 


PARTS    BENEATH    THE    STERNO-MASTOID. 


first    rib.      This   fascia    prevents   pus   coming  to  the   surface, 
when  suppuration  takes  place  by  the  side  of  the  pharynx. 

Remove  the  fascia,  and  clean  the  various  structures  beneath 
the  sterno-mastoid,  taking  care  not  to  cut  away  the  descendens 


3d  cervical  n. 

Communicans 
hypoglossi  n. 

Crico-thyroid 


Internal  juga 

lar  V. 
Common  car^ 

odd  a. 


Digastricus. 

Junction  of 
mylo-hyoidei. 


— ■  N.Acessorius. 
Os  hyoides. 


Pomum 
Ad  ami. 


_     Crico-tliyroiil 
membrane. 

Cricoid    carti- 
lage. 

Isthmus  of 
—       thyroid 
gland. 


Trachea. 


Inferior 
thyroid  v. 


Fig.  36.  —  Central  Line  op  Neck.  —  Course  and  Relations  of  Common  Carotiij  Aktehy. 


hypoglossi  and  communicantes  hypoglossi  nerves,  which  lie  in 
front  of  the  sheath  of  the  common  carotid.  Dissect  out  the 
lymphatic  glands  which  lie  along  the  sheath  of  the  large 
vessels. 

Parts    exposed    beneath  the   Sterno-mastoid.  —  The  ob- 
jects exposed  to  view,  when  the  muscle  is  reflected,  are  very 


PARTS    BENEATH    THE    STERNO-MASTOID. 


95 


numerous.  Among  these  the  more  important  are  :  the  sterno- 
cla\'icular  articulation,  the  splenius  capitis  and  colH,  the  poste- 
rior belly  of  the  digastric,  the  levator  anguli  scapulae,  scalenus 
medius  and  anticus,  omo-hyoid,  sterno-hyoid,  and  sterno-thyroid 
muscles  ;  the  occipital  artery,  the  common  carotid  artery  and 
its  division,  the  internal  jugular  vein,  the  subclavian  artery  and 
the  branches  of  the  first  part  of  its  course,  the  cervical  plexus, 


Fig.  37.  —  Muscles  of  the  Hyoid  and  Infra-hyoid  Regions. 
I.  Posterior  belly  of  the  digastric  m.  2.  Stylo-hyoid  m.  3.  Anterior  belly  of  the  digastric  m. 
4.  Tendon  and  pulley  of  this  muscle.  5.  Anterior  belly  of  the  right  digastric  m.  6.  Mylo- 
hyoid m.  7.  Hyo-glos.-ius  m.  8.  Sternal  portion  of  the  right  sterno-mastoid  m.  g.  Sternal 
portion  of  the  left  sterno-mastoid  m.  10.  Sterno-hyoid  m.  n.  Tendon  of  the  omo-hyoid  m. 
12.  Thyro-hyoid  m.  13.  Sterno-thyroid  m.  A.  Oblique  line  of  the  thyroid  cartilage  to 
which  the  two  preceding  muscles  are  attached.  14.  Inferior  constrictor  m.  of  the  pharynx. 
15.  Trachea.  16.  fEsophagus.  17.  Rectus  capitis  anticus  major  m.  18.  Longus  colli  m. 
19.  Scalenus  anticus  m.  20,20.  Scalenii  medius  and  posticus  mm.  21,21.  Fasciculi  of  the 
levator  anguli  scapula;  m.  passing  to  be  inserted  to  the  transverse  processes  of  the  cervical  ver- 
tebrae. 22.  Splenius  capitis  m.  23.  Splenius  colli  m.  24.  Trapezius  m.  25.  Attachment 
of  the  sterno-mastoid  m.  26.  Attachment  of  the  two  fasciculi  of  the  retrahends  aurem  m. 
27.  Occipito-frontalis  m.  28.  Deltoid  m.  29.  Attachment  (sternal)  of  the  right  and  left  pec- 
toralis  major  mm.    30.    Intercostal  muscles. 

and  the  lower  cervical  nerves  which  form  the  brachial  plexus  ; 
the  phrenic,  pneumogastric,  hypoglossal,  and  spinal  accessory 
nerves,  the  descendens  and  communicantes  hypoglossi  nerves ; 
the  subclavian  vein  and  its  tributaries  ;  and  lastly,  a  small  part 
of  the  parotid  gland,  and  the  three  sterno-mastoid  arteries.  On 
the  left  side,  in  addition,  we  find  the  thoraic  duct ;  on  the  right 
side,  the  right  lymphatic  duct. 


96  COMMON  CAROTID  ARTERY. 

Course  and   Relations  of  the  Common  Carotid.  —  The 

cor,ii)io)i  carotid  artery  is  now  exposed  in  the  whole  extent  of  its 
course  in  the  neck.  It  arises,  on  the  right  side  from  the  arteria 
innominata,  behind  the  upper  part  of  the  right  sterno-clavicular 
articulation ;  on  the  left,  from  the  arch  of  the  aorta.  It  ascends 
in  front  of  the  bodies  of  the  cervical  vertebrae,  by  the  side  of 
the  trachea,  thyroid  gland,  and  larynx,  as  high  as  the  upper 
border  of  the  thyroid  cartilage,  and  then  divides  into  the 
external  and  internal  carotids.  Sui-gical  landmarks.  —  Thus,  a 
line  drawn  from  the  sternal  end  of  the  clavicle  to  a  point  mid- 
way between  the  mastoid  process  and  the  angle  of  the  mandible 
will  nearly  indicate  its  course.  It  is  contained  in  a  sheath  of 
the  deep  cervical  fascia,  together  with  the  internal  jugular  vein 
and  the  pneumogastric  nerve.  The  vein  lies  on  the  outer  side 
of,  and  parallel  with,  the  artery ;  the  nerve  lies  behind  and 
between  the  artery  and  the  vein.  The  structures  contained 
within  this  sheath  are  separated  from  each  other  by  a  thin 
septum  of  fascia,  so  that  each  has  a  separate  investment. 
Owing  to  the  increasing  breadth  of  the  larynx,  the  two  common 
carotid  arteries,  which  at  their  origin  lie  near  together,  are 
separated  by  a  wide  interval  at  their  point  of  division. 

At  the  lower  part  of  the  neck  the  carotid  artery  is  deeply 
placed,  but  as  it  ascends  it  becomes  more  superficial,  although 
it  has  the  appearance  of  being  deeply  situated  owing  to  the 
prominence  of  the  thyroid  cartilage.  In  front  the  artery  is 
covered  by  the  skin,  superficial  fascia,  platysma  myoides,  deep 
fascia,  the  sternal  portion  of  the  sterno-mastoid,  the  sterno- 
hyoid, and  thyroid  muscles,  and,  on  a  level  with  the  cricoid 
cartilage,  it  is  crossed  by  the  omo-hyoid.  Above  this  point  the 
artery  becomes  more  superficial,  and  is  covered  by  the  integu- 
ment, platysma,  the  cervical  fasciae,  the  middle  sterno-mastoid 
artery,  and  only  slightly  overlapped  by  the  sterno-mastoid. 
Lying  upon  the  sheath  of  the  artery,  we  find  the  descendens 
hypoglossi  joined  by  the  communicantes  hypoglossi  nerves. 
The  sheath  is  crossed  by  the  facial,  the  superior,  and  middle 
thyroid  veins,  and  lower  down  by  the  anterior  jugular  vein,  all 
of  which  empty  themselves  into  the  internal  jugular.  This  is 
the  general  rule,  and  especial  attention  should  be  directed  to  it, 
because  the  veins  are  liable  to  be  overlooked  and  injured  in  the 
operation  of  tying  the  carotid.  To  the  inner  side  of  the  artery 
we  find  the  trachea,  the  thyroid  body,  the  recurrent  laryngeal 
nerve,  the  inferior  thyroid  artery,  the  external  laryngeal  nerve, 


COMMON  CAROTID  AKTKKV. 


97 


the  inferior  constrictor  of  the  pharynx,  and  the  larynx.  On  the 
outer  side  are  the  pneumogastric  nerve  and  the  internal  jugular 
Behind  the  artery  are  the  sympathetic  nerve,  the  inferior 


vein. 


thyroid  artery,  the  recurrent  laryngeal  nerve  ;  and  lastly,   the 


Fig  38. — Relations  of  the  Cartoid  Arteries. 
I.  Subclavian  artery  2  Subclavian  vein  3,  •;  Common  caiotid  artery.  4  Interna!  jugular 
vein.  5.  Anterior  jugulai  vein  parsing  in  front  of  the  common  carotid  artery  to  empty  into 
lower  part  of  the  jugular  vein.  6.  Omo-hyoid  muscle.  7.  Sterno-hyoid  muscle.  8.  Trunk 
of  the  pneumogastric  nerve  placed  behind  the  carotid  and  internal  jugular,  which  it  accom- 
panies throughout  their  course  and  is  seen  between  them  interiorly.  9.  Hypoglossal  nerve. 
10.  Terminal  portion  of  the  same.  11.  Its  descending  branch  (descendens  hypoglossi  nerve). 
12.  Descending  branch  from  cervical  plexus  uniting  with  the  preceding  (communicans  hypo- 
glossi nerve).  13.  Plexus  or  ansa  formed  by  the  union  of  the  two  preceding  nerves.  14.  Internal 
carotid  artery.  15.  Superior  thyroid  artery  and  vein.  Lingual  and  facial  arteries  arising  by  a 
common  trunk.  17.  Facial  artery  and  vein.  18.  Occipital  artery.  19.  Anterior  branches  of 
the  fourth  pair  of  cervical  nerves.     20.   Superior  laryngeal  nerve. 

carotid  sheath  lies   successively  upon  the  longus  colli  and  the 
rectus  capitis  anticus  major  muscles.* 

*  It  i.s  important  that  we  should  Ije  aware  that  the  common  carotids  vary  occa- 
sionally in  their  origin.     Thus  the  right  may  arise  in  common  with  the  left  carotid, 


98  LIGATION    OF    CAROTID. 

Ligation  of  Carotid.  —  The  common  carotid  may  be  liga- 
tured  either  above  or  below  the  omo-hyoid.  It  is  most  acces- 
sible above  the  point  where  this  muscle  crosses  ;  and  therefore, 
if  the  surgeon  has  his  choice,  he  would  prefer  to  tie  the  vessel 
in  this  situation.  In  the  higher  operation  we  make  an  incision, 
three  inches  ij .6  cm.)  in  length,  along  the  inner  border  of  the 
sterno-mastoid,  the  centre  of  the  incision  being  opposite  the 
cricoid  cartilage  ;  we  cut  through  the  skin,  superficial  fascia, 
platysma,  deep  cervical  fascia,  when  we  come  to  the  anterior 
border  of  the  sterno-mastoid.  The  overlapping  edge  of  this 
muscle  must  be  drawn  outwards,  and  the  muscle  at  the  same 
time  relaxed  by  turning  the  head  to  the  same  side.  The  sheath 
of  the  vessel  is  then  exposed,  and  a  small  opening  is  to  be 
made  on  its  inner  side  large  enough  to  admit  the  aneurism 
needle,  which  should  be  passed  round  the  artery  on  its  outer 
side,  so  as  to  avoid  wounding  the  internal  jugular  vein.  The 
vessel  is  then  to  be  ligatured,  care  being  taken  not  to  separate 
more  of  the  sheath  than  is  necessary"  from  the  artery,  and  not 
to  include  in  the  ligature  the  pneumogastric  or  descendens  hy- 
poglossi  nerves. 

Collateral  circulation  established.  —  After  ligation  of  the 
artery,  the  collateral  circulation  is  maintained  by  the  following 
vessels  :  between  the  branches  of  the  external  and  internal 
carotid  arteries  of  the  opposite  side  with  the  corresponding 
branches  of  the  ligatured  side  ;  between  the  vertebral  and  the 
posterior  communicating  of  the  same  side ;  between  the  inferior 
and  superior  thyroids  of  the  same  side ;  between  the  profunda 
cervicis  and  the  princeps  cervicis  of  the  occipal  of  the  same  side. 

In  what  respects  the  Left  Carotid  differs  from  the 
Right.  —  In  the  first  part  of  its  course  the  left  carotid  differs 
from  the  right  in  the  following  particulars :  — 

I.  It  arises  from  the  arch  of  the  aorta,  is  therefore  longer 
and  deeper  seated  than  the  right,  and  is  covered  by  the  first 
bone  of  the  sternum. 

or  the  right  may  arise  separately  from  the  arch  of  the  aorta,  in  which  case  the 
right  sul)clavian  is  usually  transposed.  The  left  may  be  given  off  from  the  in- 
nominate artery  of  the  right  side,  or  it  rnay  arise  in  common  with  the  left  sub- 
clavian, and  thus  form  a  left  innominate.  In  transposition  of  the  aorta  there  is  a 
left  innominate,  which  is  given  off  first,  the  right  carotid  and  the  right  subclavian, 
arising  as  separate  branches  from  the  arch.  The  ])lace  of  division  of  the  common 
carotid  is  subject  to  con.siderable  variation  ;  it  may  divide  higher  or  lower  than 
usual,  the  former  being  the  more  frequent.  Rarely  there  has  been  no  common 
carotid  artery,  tiie  external  and  internal  arising  as  separate  branches  from  the  arch 
of  the  aorta. 


INTERNAL    JUGULAR    VEIN.  99 

2.  It  is  crossed  by  the  left  brachio-ccphalic  vein. 

3.  It  is  in  close  relation  with  the  oesophagus  and  the  trachea. 

4.  It  is  in  close  relation  with  the  left  recurrent  laryngeal 
nerve. 

5.  It  is  in  close  relation  posteriorly  with  the  thoracic  duct. 

6.  It  is  covered  by  the  thymus  gland  in  early  life. 

The  artery  has  in  front  the  sternum,  the  sterno-hyoid  and 
stcrno-thyroid  muscles,  the  left  innominate  vein,  and  the  remains 
of  the  thymus  gland  ;  to  the  left  side  it  has  the  left  subclavian 
artery  and  the  left  pneumogastric  nerve  ;  to  the  right  side  the 
arteria  innominata ;  and  beJiind,  the  trachea,  oesophagus,  and 
thoracic  duct. 

The  common  carotid,  as  a  rule,  gives  off  no  branch  in  its  course ;  but,  occasion- 
ally, the  middle  sterno-mastoid,  the  superior  thyroid,  or,  more  rarely,  the  vertebral, 
arise  from  it  prior  to  its  division.  At  its  bifurcation  it  usually  presents  a  slight 
bulbous  enlargement,  which  is  sometimes  so  marked  that  it  might  be  mistaken  for 
an  incipient  aneurism.  It  is  necessary  to  know  that  the  carotid  sometimes  divides 
as  low  as  the  level  of  the  cricoid  cartilage,  and  that  not  infrequently  the  division 
takes  place  as  high  as  the  hyoid  bone. 

Internal  Jugular  Vein.  —  The  internal  jugular  vein  is  the 
continuation  of  the  lateral  sinus,  and  returns  the  blood  from  the 
brain.  Leaving  the  skull  through  the  foramen  jugulare,  it  re- 
ceives the  inferior  petrosal  sinus,  and  at  the  junction  it  presents 
a  slight  enlargement,  the  sinus.  The  vein  descends  on  the 
outer  side  of  the  internal  carotid,  and  subsequently  the  common 
carotid  arteries,  in  the  same  sheath,  and  joins  the  subclavian 
vein  at  a  right  angle  to  form  the  brachio-cephalic  or  innominate 
vein.  In  its  course  down  the  neck  it  receives  the  pharyngeal, 
occipital,  facial,  lingual,  superior,  and  middle  thyroid  veins. 

Previous  to  their  terminations  the  internal  jugular  veins  incline 
somewhat  to  the  right  side  to  meet  the  corresponding  subcla- 
vian veins ;  thus,  on  the  right  side,  there  is  a  triangular  interval 
between  the  artery  and  vein  in  which  is  seen  the  pneumogastric 
nerve  and  vertebral  artery ;  on  the  left  side  the  vein  slightly 
overlaps  the  artery,  thus  rendering  ligature  of  the  left  carotid 
more  difficult  than  of  the  right.  The  internal  jugular  veins, 
moreover,  advance  slightly  to  meet  the  subclavian  veins,  so  that 
they  lie  on  a  plane  a  little  anterior  to  their  accompanying  arte- 
ries. A  little  before  their  termination  the  internal  jugulars 
have  a  double  valve. 

Descendens  Hypoglossi  and  Communicantes  Hypoglossi 
Nerves. — The  descendens  Jiypogiossi  (p.  lOo)  runs  down  obliquely 
over  the  sheath  of  the  carotid  to  supply  the  depressor  muscles 


lOO 


COMMUNICANTES    HYPOGLOSSI    NERVES. 


of  the  OS  hyoides.  Trace  the  nerve  upwards  to  see  that  it 
leaves  the  hypoglossal  where  this  nerve  curves  round  the  occipi- 
tal artery.  For  a  short  distance  the  descendens  hypoglossi  lies 
within  the  carotid  sheath  ;  but,  about  the  level  of  the  os  hyoides, 


<  )ccipital  a. 

Hypoglossal 
n. 

Descendens     . 

hypoglossi  n. 

2d  cervical  n. 

Superior    thy- 
roid a. 

3d  cervical  n. 

Conimunicans 
hypoglossi  n. 
Crico-thyroid 

m. 
Internal  jugu- 
lar V. 
Common  car- 
otid a. 


Digastricus. 

Junction  of 
mylo-hyoidei. 


N.Acessorius. 


Os  hyoides. 


Cricoid    carti- 
lage. 

Isthmus  of 
thyroid 
gland. 


Trachea. 

Inferior 
thyroid  v. 


Fig.  3Q. — Central  Line  of  Neck.  —  Cour.se  and  Relations  of  Common  Carotid  Artekv. 


it  comes  through  the  sheath,  and  crosses  obliquely  over  the 
carotid,  from  the  outer  to  the  inner  side.  The  descendens 
hyglossi  is  reinforced  by  one  or  more  nerves  termed  communi- 
cantes  hypoglossi,  derived  from  the  second  and  third  cervical 
nerves.  These  communicating  branches  descend  on  the  outer 
side  of  the  mternal  jugular  vein,  and  form  generally  two  loops 


THYROID    BODY.  Id 

in  front  of  the  carotid  sheath,  constituting  a  triangular  plexus 
called  the  ''ansa  hypoglossiy  From  these  loops  the  nerves  pro- 
ceed to  the  anterior  and  posterior  bellies  of  the  omo-hyoid  to  the 
sterno-hyoid  and  sterno-thyroid  muscles.  A  small  branch  may 
sometimes  be  traced  proceeding  from  the  descendens  hypoglossi 
into  the  chest  to  join  the  cardiac  and  phrenic  nerves. 

In  some  subjects  the  descendens  hypoglossi  seems  to  be 
wanting,  in  which  case  it  will  probably  be  concealed  within  the 
carotid  sheath  ;  when  this  happens  the  reinforcing  loops  from 
the  cervical  nerves  will  be  found  behind  the  internal  jugular 
vein.* 

Dissection.  —  The  thyroid  body  should  now  be  examined. 
To  expose  it,  reflect  the  sterno-hyoid  and  thyroid  muscles  from 
their  insertions,  so  that  they  can  be  replaced  if  necessary. 
Next  observe  the  lymphatic  glands  of  the  neck,  and  lastly  sur- 
vey the  objects  in  the  central  line  of  the  neck,  from  the  mandi- 
ble to  the  sternum. 

Thyroid  Body.  —  This  very  vascular  gland-like  body  lies 
over  the  front  and  sides  of  the  upper  part  of  the  trachea,  and 
extends  upwards  on  each  side  of  the  larynx.  It  consists  of  tzvo 
lateral  lobes,  connected  a  little  below  the  cricoid  cartilage  by 
a  transverse  portion  called  the  isthmus,  and  weighs  from  one  to 
two  ounces  {28.J  gms.  to  ^6.6  gms.).  Each  lobe  is  conical,  about 
two  inches  (5  cm.)  in  length,  and  an  inch  and  a  quarter  {J. 2  cm.) 
in  breadth.  Its  base  is  opposite  the  fifth  or  sixth  ring  of  the 
trachea,  and  the  apex  by  the  side  of  the  thyroid  cartilage.  Its 
anterior  surface  is  convex,  and  is  covered  by  the  sterno-hyoid, 
sterno-thyroid,  and  omo-hyoid  muscles  ;  its  deep  surface  —  con- 
cave —  embraces  the  sides  of  the  trachea  and  larynx,  and 
usually  extends  so  far  backwards  as  to  be  in  contact  with  the 
pharynx.  Its  external  border  overlaps,  in  most  cases  partially, 
but  sometimes  completely,  the  common  carotid  artery,  particu- 
larly on  the  right  side  ;  and  there  are  instances  in  which  the 
lobe  is  deeply  grooved  by  the  vessel. 

Surgical  Landmarks.  —  The  isthmus  lies  over  the  second 
and  third  rings  of  the  trachea.  This  portion  of  the  organ  varies 
much  in  its  dimensions.     In  some  instances  there  is  no  trans- 


*  By  many  anatomists  the  descendens  hypoglossi  is  regarded  as  the  combina- 
tion of  filaments  from  the  hypoglossal  and  pneumogastric  nerves;  by  some  it  is 
looked  upon  as  a  branch  of  the  pneumogastric  ;  and  lastly,  which  is  most  prob- 
able, it  is  considered  by  others  to  be  mainly  derived  from  a  branch  which  is  sent 
to  the  hypoglossal  from  the  first  and  second  cervical  nerves. 


I02  SURGICAL    LANDMARKS. 

verse  portion.  This  corresponds  with  the  normal  disposition  in 
most  of  the  lower  orders  of  mammalia  ;  but  in  man,  it  is  a  failure 
in  the  union  of  the  two  halves  by  which  the  organ  is  originally 
developed.*  Generally,  the  vertical  measurement  is  about  half 
an  inch  (/J  mm.).  Between  its  upper  border  and  the  cricoid 
cartilage  is  a  space  about  one-third  of  an  inch  {8.J  mm)  in 
extent,  where  the  trachea  is  free;  this  space,  therefore,  is  the 
more  preferable  situation  for  tracheotomy.  But  the  vertical 
measurement  of  this  isthmus  is  sometimes  of  very  considerable 
length,  so  that  it  has  been  seen  covering  the  trachea  almost 
down  to  the  sternum. f 

The  thyroid  body  is  closely  connected,  by  areola  tissue,  to 
the  sides  of  the  trachea,  to  the  cricoid  and  thyroid  cartilages. 
Hence  it  rises  and  falls  with  the  larynx  in  deglutition. 

The  thyroid  varies  in  size  in  different  individuals  and  at  dif- 
ferent periods  of  life.  It  is  relatively  larger  in  the  child  than 
the  adult,  in  the  female  than  the  male.  In  old  age  it  diminishes 
in  size,  becomes  firmer,  and  occasionally  contains  earthy  matter. 

By  far  the  most  notable  considerations  in  respect  to  the  thy- 
roid body  are  the  number,  the  large  size,  and  the  free  inoscula- 
tions of  its  arteries.  The  superior  thyroid  arteries  come  from 
the  external  carotid,  and  enter  the  front  surface  of  the  apex  of 
each  lobe ;  the  inferior  thyroid  come  from  the  subclavian,  and 
enter  the  under  surface  of  the  base.  An  artery,  called  the 
middle  thyroid  (thyroidea  ima),  is  observed  in  some  subjects ; 
it  is  given  off  from  the  arteria  innominata,  or  the  arch  of  the 
aorta,  and  ascends  directly  in  front  of  the  trachea  to  the  isthmus. 

Its  veins  are  equally  large,  and  form  a  plexus  upon  it.  The 
superior  and  middle  thyroid  veins  cross  the  common  carotid, 
and  open  into  the  internal  jugular.     The  inferior  thyroid  veins, 

*  Concerning  the  development  of  the  lateral  halves  and  central  portion  of  the 
thyroid  body,  see  a  paper  by  Callender  in  the  Proceedings  of  the  Royal  Society, 
1867. 

t  From  the  upper  part  of  the  isthmus,  or  from  the  adjacent  border  of  either 
lobe,  most  commonly  the  left,  a  conical  prolongation  of  the  thyroid  body,  called 
the  pyrairiid.,  frequently  ascends  in  front  of  the  crico-thyroid  membrane,  as  high 
as  the  pomum  Adami,  and  is  attached  to  the  body  of  the  os  hyoides  by  fibrous 
tissue.  In  some  subjects  we  may  observe  a  few  muscular  fibres  passing  from  the 
OS  hyoides  to  the  pyramid.  This  constitutes  the  levator  glandula:  thyroidea  (see 
preparation  in  Museum  of  St.  Earth.  IIosp.,  Patholog.  Series,  No.  14)  of  some 
anatomists.  There  are  instances  in  which  the  pyramid  is  double;  and,  lastly,  we 
have  seen  a  considerable  portion  of  this  thyroid  substance  lying  over  the  crico- 
thyroid membrane,  completely  isolated  from  the  rest  of  the  organ.  These  varie- 
ties deserve  notice,  because  any  one  portion  of  this  .structure  may  become  enlarged 
independently  of  the  rest,  and  occasion  a  bronchocele. 


DEEP    CERVICAL    LYMPHATIC    GLANDS.  IO3 

two  ill  number,  descend  over  the  front  of  the  trachea,  commu- 
nicate freely  with  each  other,  and  terminate  in  the  left  brachio- 
cephalic vein.  When  you  perform  tracheotomy,  bear  in  mind 
the  size  of  these  inferior  thyroid  veins,  and  the  possible  exis- 
tence of  a  middle  thyroid  artery. 

Its  nc>"<cs  are  furnished  by  the  middle  and  inferior  cervical  ganglia  of  the  sym- 
pathetic.    They  accompany  the  arteries. 

The  Ivmphatics  of  the  thyroid  body  are  both  numerous  and  large.  They  form 
a  dense  network  on  the  surface,  and  pass  into  the  connective  tissue  of  the  gland, 
and  eventually  "enclose  the  primary  lobes  in  complete  rings  or  more  or  less  per- 
fect arches."  On  the  right  side  they  open  into  the  right  lymphatic  duct,  on  the 
left  side  into  the  thoracic  duct. 

Structure  of  the  Thyroid  Body. — The  thyroid  body  be- 
longs to  the  class  of  ductless  glands,  since  no  excretory  duct 
has  been  discovered.  It  is  invested  by  a. thin  covering  of  dense 
areolar  tissue,  which  connects  it  with  the  surrounding  structures 
and  also  penetrates  it,  imperfectly  dividing  it  into  lobes  and  sup- 
porting the  vessels  as  they  enter  it.  It  consists  of  a  multitude 
of  closed  vesicles,  which  are  imbedded  in  a  delicate  reticulum. 
The  function  of  the  gland  is  probably  that  of  disintegration  of 
the  red  blood-cells,  and  of  the  conveyance  into  the  general  lym- 
phatic system  of  the  products  of  these  degenerative  changes. 

Relations  of  the  Thyroid  in  Disease. — An  enlargement 
of  the  thyroid  body  is  termed  a  "  bronchocele."  If  the  relation 
of  its  lobes  to  the  trachea  and  oesophagus  be  properly  under- 
stood, it  is  easy  to  predicate  the  consequences  which  may  result 
from  their  enlargement.  The  nature  and  severity  of  the  symp- 
toms will,  to  a  certain  extent,  be  determined  by  the  part  of  the 
organ  affected.  An  enlargement  of  the  left  lobe  is  more  likely 
to  produce  a  difficulty  in  swallowing,  on  account  of  the  inclina- 
tion of  the  oesophagus  towards  the  left  side.  If  the  isthmus  be 
enlarged,  difficulty  in  breathing  will  probably  be  the  prominent 
symptom,  and,  in  order  to  remove  this  danger,  the  isthmus  has 
been  divided,  and  in  part  removed. 

Small  lymphatic  glands  are  observed  about  the  thyroid  body,  especially  in  front 
of  the  trachea;  one  is  often  situated  over  the  cricothyroid  membrane.  These 
glands,  if  enlarged  by  disease,  might  be  taken  for  a  small  bronchocele. 

Deep  Cervical  Lymphatic  Glands.  —  In  the  connective 
tissue  which  surrounds  the  great  vessels  of  the  neck,  we  meet 
with  a  series  of  lymphatic  glands,  called  the  deep  cervical.  They 
form  an  uninterrupted  chain  (whence  their  name  glanduI(Z 
concatcnatce),  from  the  base  of  the  skull,  along  the  side  of  the 


104  DEEP    CERVICAL    LYMPHATIC    GLANDS. 

neck,  to  the  clavicle,  beneath  which  they  are  continuous  with 
the  thoracic  and  the  axillary  glands.  Some  of  these  glands  lie 
anterior  to  the  common  carotid  artery  ;  others,  between  it  and 
the  spine.  This  disposition  explains  the  well-known  fact,  that, 
when  these  glands  are  enlarged,  the  great  vessels  and  nerves  of 
the  neck  are  liable  to  become  imbedded  in  their  substance. 


Fig.  40.  —  Lymi'iiatic  Vessels  Coming  from  thb  GlaiStds  of  this  Neck  and  Axilla. 

I.  Superior  extremity  of  the  thoracic  duct  passing  behind  the  internal  jugular  vein,  in  an  arch. 
2.  'J"erminal  |)ortion  of  this  arch,  wliich  enters  in  the  angle  made  by  the  union  of  the  internal 
jugular  and  the  subclavian  veins  on  the  left  side. 

The  glands  are  particularly  numerous  near  the  division  of  the  common  carotid, 
by  the  side  of  the  pharynx,  and  the  posterior  belly  of  the  digastricus.  The  lym- 
phatics connected  with  them  come  from  all  parts  of  the  head  and  neck.  These 
vessels  unite,  to  form,  on  both  sides  of  the  neck,  one  or  more  absorbent  ti"unks, 
called  the  jugular.  On  the  left  side  this  jugular  trunk  joins  the  thoracic  duct,  or 
opens  by  a  separate  orifice  into  the  junction  of  the  left  internal  jugular  and  sub- 
clavian veins;  on  the  right  side  it  opens  into  the  right  lymphatic  duct,  a  short 
trunk  about  half  an  inch  in  length,  which  terminates  at  the  angle  of  the  junction 
of  the  right  internal  jugular  and  subclavian  veins.     The  terminations  of  the  tho- 


SURGICAL  RELATIONS  IN  TRACHEOTOMY.         IO5 

lacic  duct  and  the  right  lymphatic  duct  are  guarded  by  two  small  semilunar  valves, 
in  order  to  prevent  regurgitation  of  blood  back  from  tlie  veins. 

The  contiguity  of  the  glands  to  the  great  vessels  and  nerves  of  the  neck  ex- 
plains the  symptoms  produced  by  their  enlargement.  The  tumor  may  be  so  sit- 
uated as  to  be  raised  and  depressed  by  the  pulsation  of  the  carotid,  and  thus 
stimulate  an  aneurism.  A  careful  e.xamination,  however,  will  distinguish  between 
an  inherent  and  a  communicated  pulsation.  By  grasping  the  tumor  we  become 
sensible  that  the  pulsation  does  not  depend  upon  any  variation  of  its  magnitude, 
but  upon  the  impulse  derived  from  the  artery ;  consequently,  if  the  tumor  be 
lifted  from  the  vessel,  all  feeling  of  pulsation  ceases. 

Survey  of  the  Central  Line  of  the  Neck.  —  The  parts  in 
the  central  line  of  the  neck  should  now  be  well  studied  (Fig.  39, 
p.  100).  Beginning  at  the  chin,  we  observe  the  insertions  of  the 
digastric  muscles.  Below  these  is  the  junction,  or  raphe,  of 
the  mylo-hyoid  muscles.  Then  comes  the  os  hyoides.  Below 
the  OS  hyoides  is  the  thyro-hyoid  membrane,  attached  above 
to  the  posterior  and  upper  border  of  the  hyoid  bone,  and  below 
to  the  thyroid  cartilage.  Next  is  the  pomum  Adami,  or  pro- 
jection of  the  thyroid  cartilage,  which  is  apparent  between  the 
contiguous  borders  of  the  sterno-hyoidei.  Below  the  thyroid 
cartilage  is  the  cricoid.  These  two  cartilages  are  connected  by 
the  crico-thyroid  membrane,  across  which  runs  the  crico-thyroid 
artery  to  join  its  fellow.  Below  the  cricoid  cartilage  is  the 
trachea.  This  is  crossed  by  the  isthmus  of  the  thyroid  body, 
and  lower  down  it  recedes  from  the  surface,  covered  by  the 
inferior  thyroid  veins. 

Surgical  Relations  in  Laryngotomy.  —  Now  the  chief 
surgical  interest  lies  just  above,  and  just  below,  the  cricoid  car- 
tilage. This  cartilage  can  be  felt  very  plainly  in  the  living 
subject  at  any  age,  no  matter  how  fat.  In  laryngotomy,  the 
crico-thyroid  membrane  is  divided  transversely.  The  membrane 
should  be  divided  close  to  the  edge  of  the  cricoid  c,  for  two 
reasons  :  i.  In  order  to  be  farther  from  the  vocal  cords.  2.  To 
avoid  the  crico-thyroid  artery,  which  crosses  the  middle  of  the 
membrane.  If  more  room  is  required,  the  cricoid  cartilage 
should  be  divided  longitudinally. 

Surgical  Relations  in  Tracheotomy.  —  In  tracheotomy, 
the  trachea  may  be  opened  by  a  perpendicular  incision,  above 
the  isthmus  of  the  thyroid  body,  or  below  it.  The  operation 
above  the  isthmus,  if  there  be  space  enough  for  the  introduc- 
tion of  the  tube,  is  the  easier  and  safer  of  the  two;  for  here 
the  trachea  is  nearer  to  the  surface,  and  no  large  blood-vessels 
are,  generally  speaking,  in  the  way.  The  space  available  meas- 
ures from  a  quarter  {p.2  vim.)  to  half  {12.^  mm)  an  inch ;  and 


I06  DIGASTRIC    TRIANGLE. 

the  isthmus  is  not  so  firmly  adherent  to  the  trachea  as  to 
prevent  its  being  drawn  downwards  for  a  short  distance. 
However,  it  is  right  to  state  that,  in  one  case  out  of  every 
eight  or  ten,  there  is  no  available  space. 

Tracheotomy  below  the  isthmus  is  neither  an  easy  nor  a  safe 
operation,  for  many 'reasons  :  i.  The  trachea  recedes  from  the 
surface  as  it  descends,  so  that  just  above  the  sternum  it  is  nearly 
an  inch  and  a  half  ( J.cS*  cm.)  from  the  skin.  2.  The  large  in- 
ferior thyroid  veins  are  in  the  way.  3.  A  middle  thyroid  artery 
may  run  up  in  front  of  the  trachea,  direct  from  the  arteria  in- 
nominata.  4.  The  arteria  innominata  itself  lies  sometimes 
upon  the  trachea  higher  than  usual,  and  may,  therefore,  be  in 
danger.  5.  The  left  brachio-cephalic  vein  in  seme  cases 
crosses  the  trachea  above  the  edge  of  the  sternum  instead  of 
below  it. 

Whoever  pays  attention  to  this  subject  in  the  dissecting-room 
will  soon  be  convinced  of  the  fact  that  not  only  large  veins,  but 
large  arteries,  occasionally  cross  the  crico  thyroid  membrane  as 
well  as  the  trachea,  thus  showing  the  necessity  of  cutting 
cautiously  down  to,  and  fairly  exposing,  the  air  tube  before  _we 
venture  to  open  it.  It  is  preferable,  after  making  the  first  in- 
cision through  the  skin,  to  lay  aside  the  sharp  knife  and  to  use 
a  blunt  one,  so  that  the  tissues  may  be  torn  rather  than  cut ; 
by  this  proceeding  the  liability  to  haemorrhage  is  materially  les- 
sened. Tracheotomy  is  now  safely  done  with  the  hypodermic 
injection  of  a  5  per  cent  solution  of  hydrochlorate  of  cocaine 
with  perfect  ease  to  the  patient  and  little  or  no  danger  on  ac- 
count of  the  hremorrhage  carrying  off  the  surplus  of  the  drug. 
Ether  or  chloroform  is  not  necessary. 

Dissection  of  the  Submandibular  Region  or  the  Digas- 
tric Triangle.  —  When  the  platysma  and  the  cervical  fascia 
have  been  removed  from  their  attachment  to  the  mandible,  the 
most  conspicuous  object  is  the  submandibular  gland.  Observe 
that  the  fascia  is  here  very  strong,  and  forms  for  the  gland  a 
complete  capsule.  Beneath  the  mandible  are  several  lymphatic 
glands,  from  six  to  ten  in  number,  of  which  some  lie  superficial 
to  the  salivary  gland,  others  beneath  it.  These  glands  receive 
the  lymphatics  of  the  face,  the  tonsils,  and  the  tongue. 

A  little  dissection  will  expose  a  muscle  called  the  digastric, 
consisting  of  two  distinct  fleshy  portions  connected  by  a  tendon. 
They  form,  with  the  body  of  the  mandible,  a  triangle  called  the 
digastric,  of  which  we  propose  to  examine  the  contents.     The 


DIGASTRIC. 


107 


muscles  forming  its  floor  are  the  mylo-hyoideus  and  hyo-glossus. 
Under  the  submandibular  gland  is  the  facial  artery,  which  here 
runs  a  tortuous  course,  and  finally  turns  up  over  the  mandible 
in  front  of  the  masseter  muscle.  Lying  on  the  mylo-hyoideus, 
under  cover  of  the  mandible,  is  the  submental  artery,  accompa- 
nied by  the  mylo-hyoid  nerve  and  artery.  Behind  the  subman- 
dibular gland,  and  separating  it  from  the  parotid,  which  also  is 
contained  within  this  triangle,  is  the  stylo-mandibular  ligament. 


Facial  a. 
Mylo  hyoid  n. 


Submental  a. 


Occipital  a 


Hypoglossal  n. 

Descendens  hypo- 
glossi  n. 

Lingual  a 


Internal  jugular  v 
Superior  thyroid  a 


Common  carotid  a.  


Fig.  41.  — Digastric  Triangle  and  Contents. 

Ascending  and  then  entering  the  parotid  is  the  external  carotid 
artery,  in  front  of  which  is  the  submandibular  branch  of  the 
facial  nerve.  Deep  in  this  space  are  situated  the  internal  jugu- 
lar vein,  the  internal  carotid  artery,  and  the  pneumogastric 
nerve  ;  and  running  obliquely  forwards  between  the  internal  and 
external  carotid  arteries  are  the  stylo-glossus,  stylo-pharyngeus, 
glosso-pharyngeal  nerve,  and  the  stylo-hyoid  ligament. 

Digastric. — The  ^//^rt'i-/';'/*:  consists  of  two  muscular  bellies 


108  STYLO-HYOIDEUS. 

united  by  an  intermediate  tendon.  The  posterior  belly  an'ses 
from  the  digastric  fossa  of  the  temporal  bone,  passes  ob- 
liquely downwards,  forwards,  and  inwards,  and  then  ascends  to 
be  inserted  by  its  anterior  belly  close  to  the  symphysis  of  the 
mandible.  Raise  the  submaxillary  or  submandibular  gland  to 
see  the  intermediate  tendon  of  the  digastric  piercing  the  stylo- 
hyoid muscle,  the  angle  which  it  forms,  and  how  it  is  fastened 
by  aponeurosis  to  the  body  and  the  greater  cornu  of  the  os 
hyoides.  Observe  also  that  this  aponeurosis  —  supra-hyoid 
aponeurosis  —  is  connected  in  the  mesial  line  with  its  fellow  of 
the  opposite  side,  so  that  a  fibrous  expansion  occupies  the 
interval  between  the  anterior  portions  of  the  digastrics. 

Action.  —  The  chief  action  of  the  digastric  is  to  depress 
the  mandible.  But  if  the  mandible  be  fixed,  then  the  muscle 
raises  the  os  hyoides,  as  in  deglutition. 

The  posterior  belly  of  the  digastric  is  supplied  by  a  nerve 
from  the  facial  ;  the  anterior  belly  by  a  branch  from  the  mylo- 
hyoidean  nerve  (which  comes  from  the  third  division  of  the 
fifth  pair). 

Stylo-hyoideus.  —  The  stylo-hyoideus  arises  from  the  mid- 
dle of  the  styloid  process  of  the  temporal  bone,  and  passing 
downwards  and  forwards  is  inserted  into  the  body  of  the  os 
hyoides.  This  muscle  at  first  runs  above  the  posterior  belly  of 
the  digastric,  and  near  its  insertion  is  pierced  by  the  digastric 
tendon.  Its  nerve  is  derived  from  the  facial  close  to  its  exit 
from  the  stylo-mastoid  foramen,  in  common  with  the  branch  to 
the  posterior  belly  of  the  digastric*  Its  action  is  to  raise 
and  draw  back  the  os  hyoides. 

The  digastric  triangle  is  bounded  above  by  the  horizontal 
ramus  of  the  mandible,  and  mastoid  process  of  the  temporal 
bone ;  behind  by  the  posterior  belly  of  the  digastric  ;  and  in 
front  by  the  anterior  belly.  The  objects  to  be  examined  in  this 
triangle  are  twelve  in  number,  as  follows  :  — 

1.  Submaxillary     or     stibvtandibitlar        7.  vStylo-mandibular  ligament. 

salivary  gland.  8.  Part  of  the  parotid  gland. 

2.  Facial  vein.  9.  Part  of  the  external  carotid  artery. 
,3.   Facial  artery.                                            10.  Mylohyoideus  muscle. 

\.  Submental  artery.  11.  llypoglo.ssal  nerve. 

5.  Mylo-hyoidean  nerve.  12.  Part  of  the  hyo-glossus  muscle. 

6.  Submandibular  lymphatic  glands. 

*  In  many,  if  not  in  most  subjects,  a  small  filament  from  the  hypoglossal  nerve 
is  distributee!  to  this  muscle. 


EXTEKNAI.  CAROTID  ARTERY.  IO9 

Submaxillary  or  Submatidibidar  Salivary  Gland.  —  In 
the  ordinary  position  of  the  head,  the  submandibular  gland  is 
partially  concealed  by  the  mandible,  but  when  the  head  falls  back 
the  gland  is  more  exposed.  It  is  about  the  size  of  a  chestnut  (7 
c.  cm.  in  volume),  weighs  about  two  drachms  (8  gm.),  and  is 
divided  into  several  lobes.  Its  upper  margin  is  covered  by  the 
body  of  the  mandible ;  its  lower  margin  overlaps  the  side  of  the 
OS  hyoides.  Its  cutaneous  surface  is  flat,  being  covered  only  by 
the  skin,  platysma,  and  deep  cervical  fascia ;  but  the  lobes  on 
its  deep  surface  are  irregular,  and  often  continuous  with  those 
of  the  sublingual  gland.  By  raising  the  gland  we  find  that  it 
lies  upon  the  mylo-hyoides,  the  hyo-glossus,  the  stylo-glossus, 
the  tendon  of  the  digastric,  and  a  portion  of  the  hypoglossal 
nerve,  seen  above  the  tendon.  Part  of  the  gland  passes  beneath 
the  posterior  border  of  the  mylo-hyoid,  and  not  infrequently 
becomes  continuous  with  the  sublingual  gland.  The  facial 
artery  lies  in  a  groove  on  its  deeper  surface,  and  subsequently 
upon  its  upper  border ;  and  it  is  separated  from  the  parotid 
gland,  which  is  situated  behind  it,  by  the  stylo-mandibular  liga- 
ment. Mark  these  relations  well,  because  they  are  of  impor- 
tance, a.s  will  be  presently  explained  in  tying  the  lingual  artery. 
(See  Fig.  22,  p.  58.) 

The  duct  of  the  gland  cannot  at  this  stage  of  the  dissection 
be  traced  further,  for  it  runs  forward,  under  cover  of  the  mylo- 
hyoideus,  to  end  in  the  floor  of  the  mouth,  by  the  side  of  the 
frasnum  linguae.  The  description  of  its  course  and  relations 
had  better,  therefore,  be  deferred  till  it  can  be  dissected  in  its 
whole  length  with  the  gustatory  nerve  in  the  pterygoid  region. 

Facial  Vein.  —  The  facial  vein  does  not  accompany  the 
facial  artery,  but  runs  nearly  a  straight  course.  It  leaves  the 
face  at  the  anterior  edge  of  the  masseter  m.,  then  runs  over 
the  submandibular  gland,  the  digastric  and  stylo-hyoideus  and 
the  carotid  artery,  to  join  the  internal  jugular.     This  is  the  rule 

—  but  there  are  frequent  exceptions.  Before  it  empties  itself 
into  the  internal  jugular  it  is  joined  by  a  large  branch  from  the 
external  jugular  vein.  The  principal  point  to  remember  is,  that 
the  vein  runs  superficial  to  the  gland,  and  that  we  must  be  cau- 
tious   in    opening    abscesses    under  the    mandible.       (Fig.    38, 

P-  97-) 

Course  and  Relations  of  the   External  Carotid  Artery. 

—  The  course  and  relations  of  the  external  carotid  artery,  and 
its  branches  in  the  neck,  should  now  be  made  out  as  far  as  the 


IIO  EXTERNAL  CAROTID  ARTERY. 

parotid  gland.  In  preparing  a  view  of  them,  observe  that  nearly 
all  the  veins  lie  in  front  of  their  corresponding  arteries.  In 
removing  the  connective  tissue,  fat,  and  lymphatic  glands  the 
student  must  take  care  of  the  nerves  and  other  structures  which 
are  liable  to  be  injured. 

The  external  carotid  arises  from  the  common  carotid  about 
the  level  of  the  upper  border  of  the  thyroid  cartilage.  It  as- 
cends to  the  interval  between  the  ear  and  the  mandible  in  a 
slightly  curved  direction,  at  first  forwards  and  then  backwards. 
The  external  and  the  internal  carotids  are  in  the  adult  nearly  of 
equal  size  ;  but  the  external  rapidly  diminishes  in  size,  owing  to 
the  large  branches  it  gives  off  within  a  short  distance.  At  first 
it  lies  beneath  the  skin,  superficial  fascia,  platysma  myoides, 
deep  cervical  fascia,  some  of  the  superficial  cervical  nerves,  and 
the  sterno-mastoid  muscle.  It  is  next  crossed  by  the  hypo- 
glossal nerve,  the  facial  and  lingual  veins,  the  posterior  belly  of 
the  digastric  and  stylo-hyoideus ;  it  then  enters  the  parotid 
gland,  where  it  lies  beneath  the  facial  nerve  and  the  external 
jugular  vein,  and  terminates  between  the  external  auditory 
meatus  and  the  neck  of  the  mandible,  by  dividing  into  the 
temporal  and  internal  maxillary  arteries.  Internally  the  artery 
is  in  relation  with  the  hyoid  bone,  the  pharynx,  the  parotid 
gland,  and  the  posterior  border  of  the  ascending  ramus  of  the 
mandible. 

Behind  i\\Q  external  carotid,  and  separating  it  from  the  inter- 
nal, are  the  stylo-glossus,  the  stylo-pharyngeus,  the  glosso-pha- 
ryngeal  nerve,  and  the  stylo-hyoid  ligament.  The  superior 
laryngeal  nerve  and  part  of  the  parotid  gland  are  also  placed 
behind  the  artery. 

Notice  the  relative  position  which  the  external  and  internal 
carotids  bear  to  each  other.  The  external  lies  at  first  on  the 
same  plane  with,  but  nearer  to  the  side  of  the  pharynx  than  the 
internal.  It  soon,  however,  changes  its  position,  and  crosses 
obliquely  in  front  of  the  internal  to  reach  the  space  between 
the  angle  of  the  mandible  and  the  mastoid  process.  The  inter- 
nal carotid  ascends  perpendicularly  by  the  side  of  the  pharynx 
to  the  base  of  the  skull. 

The  external  carotid  gives  off  the  following  branches  :  *  — 

*  These  may  ])e  divided  into  four  sets:  those  passing  fonvard,  or  ventral ;  su- 
perior thyroid,  linmial,  facial  ;  backward,  or  dorsal ;  occipital,  posterior  auricular; 
ascending  or  cephalad ;  ascending  pharyngeal,  and  terminal,  temporal,  internal 
maxillary.     A.  H. 


SUPERIOR  THYROID  ARTERV.  Ill 

1.  The  superior  thyroid.  5.  The  posterior  auricular. 

2.  The  lingual.  6.  The  internal  ma.xillary. 

3.  The  facial.  7.  The  temporal. 

4.  The  occipital.  8.  The  ascending  pharyngeal. 

Superior  Thyroid  Artery.  —  The  superior  thyroid,  the  first 
branch  of  the  external  carotid,  arises  just  below  the  great  cornu 
of  the  OS  hyoides.  It  lies  in  the  superior  carotid  triangle,  and, 
curving  downwards  and  inwards,  runs  beneath  the  omo-hyoid, 
sterno-hyoid,  and  sterno-thyroid  muscles  to  the  upper  and  front 
surface  of  the  thyroid  body,  in  which  it  terminates.  Its 
branches  are  the  four  following  :  — 

I.  The  hyoid,  a  small  muscular  branch,  runs  horizontally  inwards  below  the 
greater  cornu  of  the  os  hyoides,  and  anastomoses  with  its  fellow. 

2.  The  superior  laryngeal  branch,  accompanied  by  the  superior  laryngeal  nerve, 
runs  inwards  beneath  the  thyro-hyoid  muscle,  pierces  the  thyrohyoid  membrane 
(sometimes  the  thyroid  cartilage),  supplies  the  muscles  and  the  mucous  membrane 
of  the  larynx,  and  anastomoses  with  its  fellow  of  the  opposite  side. 

3.  The  viiildle  sfcriio-mastoid,  a  small  branch,  variable  as  to  origin,  descends 
over  the  sheath  of  the  common  carotid  artiery,  and  enters  the  under  aspect  of  the 
sterno-mastoid  muscle. 

4.  The  crico-thyroid,  an  artery  of  great  interest  in  reference  to  the  operation  of 
laryngotomy,  crosses  the  crico-thyroid  membrane,  and  communicates  with  a  corre- 
sponding branch  on  the  opposite  side.  One  or  two  small  branches  pass  through 
the  membrane  to  the  interior  of  the  larynx.  It  is  important  to  know  that  the 
cricothyroid  artery  often  varies  in  direction  and  size.  In  most  cases  it  is  small, 
and  runs  across  the  centre  of  the  membrane ;  we  should  therefore  be  least  likely 
to  wound  it  in  laryngotomy  by  dividing  the  membrane  close  to  the  cricoid  cartilage. 
But  it  is  by  no  means  infrequent  to  find  this  artery  of  considerable  size,  taking  an 
oblique  or  even  a  perpendicular  direction  in  front  of  the  membrane,  and  finally 
distributed  to  one  of  the  lobes  of  the  thyroid  body.  We  have  seen  several 
instances  in  which  the  membrane  was  crossed  by  the  main  trunk  of  the  superior 
thyroid.  These  facts  should  establish  the  practical  rule  in  laryngotomy,  not  to 
make  an  opening  into  the  larynx  until  it  has  been  fairly  exposed. 

Among  the  many  arterial  inosculations  about  the  thyroid 
body  are  two  which  deserve  notice  :  the  one  is  formed  between 
the  two  superior  thyroid  arteries  along  the  upper  border  of  the 
isthmus  ;  the  other  takes  place  along  the  back  part  of  the  lateral 
lobe  between  the  superior  and  inferior  thyroid  arteries  of  the 
same  side. 

The  superior  thyroid  vein  leaves  the  upper  part  of  the  thyroid 
body,  crosses  over  the  common  carotid  artery,  and  joins  the 
mternal  jugular  or  the  facial  vein. 

Superior    Laryngeal    Nerve.  —  The   superior  laryngeal  nerve,   mentioned   as 

accompanying  the  superior  laryngeal  artery,  is  given  off  from  the  inferior  ganglion 
of  the  pneumogastric  nerve.  It  descends  by  the  side  of  the  pharynx,  behind  both 
carotid  arteries,  and  divides  into  two  branches  —  the  internal  and  externa!  laryn- 
geal nerves.  The  infernal  branch  enters  the  larynx  through  the  thyro-hyoid  mem- 
brane accompanied  by  the  superior  laryngeal  artery,  and   supplies  the   mucous 


112 


LINGUAL    ARTERY. 


membrane  of  the  larynx  with  its  exquisite  sensibility.  Some  of  its  branches  may 
be  traced  upwards  in  the  ar)1;eno-epig]ottideanfold  to  supply  the  epiglottis  and  the 
base  of  the  tongue  ;  others  descend  to  the  rima  glottidis  ;  a  large  branch  passes 
down  behind  the  ala  of  the  thyroid  cartilage  to  join  the  recurrent  laryngeal  nerve ; 
and  a  small  branch  pierces  the  arytenoideus  to  supply  the  mucous  membrane 
beneath  it.  The  external  branch,  descending  beneath  the  depressors  of  the  larynx, 
accompanies  the  crico-thyroid  artery,  and  after  distributing  filaments  to  the  pha- 


Occipital  a 
Hypoglossal 


Digastricus. 

Junction  of 
niylo-hyoidei. 


3d  cervical  n. 

Communicans 
hypoglossi  n 
Crico-thyroid 


Internal  jugu- 
lar V. 

Common  car- 
otid a. 


\S^ —        Trachea. 

Inferior 
thyroid  v. 


Big.  42.  —  Ckntkal  Line  ok  Neck.  —  Course  and  Relations  of  Common  Carotid  Artery. 


ryngeal  plexus,  supplies  the  thyroid  body,  the  inferior  constrictor,  and  the  crico- 
thyroid muscles.  It  receives  a  branch  from  the  superior  cervical  ganglion  of  the 
sympathetic,  and  sends  off  a  cardiac  filament  to  join  the  superior  cardiac  branch 
of  the  sympathetic  behind  the  common  carotid  artery. 

Lingual  Artery. — The  lingual  artery  and  its  branches  will 
be  described  in  the  dissection  of  the  submandibular  region. 


FACIAL    ARTERY. 


113 


Facial  Artery.  —  The  facial  artery  is  the  third  branch  of 
the  external  carotid.  It  runs  tortuously  under  the  hypoglossal 
nerve,  the  posterior  belly  of  the  digastric  and  stylo-hyoideus, 


POST.  ANT. 

.•'temporal" 


UP. 
CORONARY 


CRICO-THYROID 


MIDDLE  STERNO-MASTO 


Fig.  43.— Diagram  of  thb  Branches  of  the  External  Carotid  Artery  and  their 

Branches. 

and  beneath  or  through  the  substance  of  the  submaxillary  or 
submandibular  gland  to  the  face,  where  it  appears  at  the  ante- 
rior border  of  the  masseter.  Below  the  mandible  the  facial 
rests  on  the  mylo-hyoideus,  and  gives  off  the  four  following 
branches : 


114 


FACIAL    ARTERY. 


I.  The  ascfttdiiig  or  inferior  palatine  artery  runs  up  between  the  stylo-glossus 
and  the  stylo-pharyngeus  m.,  and  behind  the  internal  pterygoid  m.  to  the  pharynx, 
to  which  and  the  neighboring  parts  it  gives  branches.  Ascending  as  far  as  the 
levator  palati,  it  divides  into  two  branches  :  one  courses  along  the  tensor  palati  to 
supply  the  soft  palate  ;  the  other  enters  the  tonsil,  and  anastomoses  with  the 
descending  palatine  of  the  internal  maxillary,  and  with  the  tonsillar  branches  of 
the  ascendiiig  pharyngeal. 


SCNSCRY  ROOT 

AfoTOfi  floor  ^^  /    c> 


AVmCUiO  TCMPOnM  N 


Fig.  44. 


2.  The  tonsillar  runs  up  between  the  internal  pterygoid  and  the  stylo-glossus 
m. ;  then,  perforating  the  superior  constrictor,  it  supplies  the  tonsil  and  root  of 
the  tongue. 

3.  Glandular  branches  to  the  submaxillary  or  subviandibular  gland  and  side 
of  the  tongue. 

4.  The  submental  arises  from  the  facial  behind  the  submaxillary  or  subman- 
dibular gland,  and  runs  fonvards  upon  the  mylo-hyoidcus,  beneath  the  mandible, 
distributing  branches  in  its  course  to  the  gland  and  the  adjacent  muscles.  It  then 
curves  over  the  bone  and  divides  into  two  branches  :  a  superficial  one,  which  sup- 
plies the  skin  and  lip ;  and  a  deep  one,  which  runs  between  the  muscles  and  the 
bone,  and  inosculates  with  the  mental  and  inferior  labial  arteries.  Beneath  the 
mandible  it  usually  inosculates  with  the  sublingual  artery. 


STYLO-MANDIIiULAK    LICJAMENT.  II5 

The  remaining  branches  of  the  external  carotid  artery  will- be 
described  later  on. 

Mylo-hyoidean  Nerve.  —  Look  for  the  mylo-hyoidean 
nerve  near  the  submental  artery.  The  nerve  comes  from  the 
inferior  dental  (before  its  entrance  into  the  dental  foramen), 
and  running  along  a  groove  on  the  inner  side  of  the  mandible, 
advances  between  the  bone  and  the  interior  pterygoid  m.,  to 
supply  the  mylo-hyoideus  and  the  anterior  belly  of  the  digastric 

(I^^ig-  44). 

Submandibular  Lymphatic  Glands.  —  The  submandibular 

lymphatic   glands    receive  the   lymphatics  of  the  face  and  the 

tongue.     They  are   often  enlarged  in  cancerous  diseases  of  the 

tongue  or  the  lower  lip.     It   should  be  remembered  also  that 

there  are  lymphatic  glands  in  the  mesial  line  below  the  chin. 

Mylo-hyoideus. — The  mylo-hyoideus,  a  triangular  muscle, 
arises  from  the  mylo-hyoid  ridge  of  the  mandible  from  the  sym- 
physis, as  far  back  as  the  last  molar  tooth  (Fig.  41,  p.  107).  Its 
posterior  fibres  are  inserted  into  the  body  of  the  os  hyoides,  the 
anterior  being  attached  to  a  median  tendinous  line,  termed  the 
rapJii.  Thus  the  muscles  of  opposite  sides  form  a  muscular 
floor  for  the  mouth.  Superficially,  it  is  in  relation  with  the 
anterior  belly  of  the  digastricus,  the  submaxillary  or  submandib- 
ular gland,  the  submental  artery,  and  the  mylo-hyoidean  n.  By 
its  deep  surface,  it  is  in  relation  with  part  of  the  hyo-glossus, 
the  stylo-glossus,  the  genio-hyoideus,  Wharton's  duct,  the  gus- 
tatory and  hypoglossal  nerves  with  their  communications,  and 
the  sublingual  gland.  It  is  '  supplied  with  nerves  by  the  mylo- 
hyoid branch  of  the  inferior  dental ;  with  blood  by  the  sub- 
mental artery.  The  muscles  of  opposite  sides  conjointly  elevate 
the  OS  hyoides  and   the  floor  of  the   mouth  —  as  in  deglutition. 

Stylo-mandibular  Ligament.  — This  is  a  layer  of  the  deep 
cervical  fascia,  extending  from  the  angle  of  the  mandible  to  the 
styloid  process.  It  is  a  broad  sheet  of  fascia,  and  separates  the 
submandibular  gland  from  the  parotid.  It  is  continuous  with 
the  fascia  covering  the  pharynx;  this  gives  it  a  surgical  interest, 
because  it  prevents  accumulations  of  pus  formed  near  the 
tonsils  and  upper  part  of  the  pharynx  from  coming  to  the 
surface. 

The  remaining  objects  seen  in  the  submaxillary  or  S7ibman- 
dibular  triangle  —  namely,  the  parotid  gland,  the  hypoglossal 
nerve,  the  hyo-glossus  muscle  —  will  be  described  presently 
when  they  can  be  better  seen.      Your  attention  should  now  be 


I  1 6  GENIO-IIYOIDEUS. 

directed  to  a  piece  of  surgical  anatomy,  which  will  enable  you 
readily  to  find  and  tie  the  lingual  artery.      It  is  this  :  — 

A  curved  incision,  about  two  inches  (5  cm?)  in  length,  being 
made  from  the  lesser  cornu  along  the  upper  border  of  the  great 
cornu  of  the  os  hyoides,  through  the  skin,  the  platysma,  and  the 
cervical  fascia,  you  will  come  upon  the  lower  edge  of  the  sub- 
maxillary or  submandibular'  gland.  Lift  up  the  gland,  which  is 
easily  done,  and  underneath  it  you  will  observe  that  the  tendon 
of  the  digastric  makes  two  sides  of  a  triangle,  of  which  the 
base  is  formed  by  the  hypoglossal  nerve  crossing  the  hyo- 
glossus  muscle.  Within  this  little  triangle,  cut  transversely 
through  the  fibres  of  the  hyo-glossus  :  under  them  is  the  lingual 
artery,  lying  on  the  middle  constrictor.  The  first  time  you  per- 
form this  operation  on  the  dead  subject,  you  will  not  unlikely 
miss  the  artery  and  cut  through  the  middle  constrictor  into  the 
pharynx. 

Dissection.  —  The  facial  vessels  must  now  be  divided  imme- 
diately below  the  mandible.  Reflect  the  anterior  belly  of  the 
digastric  from  its  insertion ;  detach  the  mylo-hyoideus  from 
the  middle  line  and  the  os  hyoides,  and  turn  it  over  the  body  of 
the  mandible,  taking  care  not  to  injure  the  muscles  and  struc- 
tures beneath.  The  mandible  must  now  be  sawn  through,  a 
little  to  the  dissector's  side  of  the  symphysis,  and  the  bone 
drawn  upwards  by  hooks.  The  tongue  should  then  be  drawn 
out  of  the  mouth,  and  fastened  by  hooks.  The  os  hyoides 
should  be  drawn  down  by  means  of  hooks,  so  as  to  put  the  parts 
on  the  stretch.  All  this  done,  we  have  to  make  out,  by  care- 
fully cleaning  away  the  fat  and  connective  tissue,  the  following 
objects  represented  in  P'ig.  45,  p.  117: 

1.  Genio-hyoideus.  6.   Sublingual  gland. 

2.  Ilyo-glossus.  7.  Hypoglossal  nerve. 

3.  Styloglossus.  8.  Gustatory  nerve. 

4.  Genio-hyo-glossus.  9.  Submandibular  ganglion. 

5.  Submandibular  duct.  10.  Lingual  artery. 

Genio-hyoideus.  —  The  genio-hyoideus  arises  from  the  in- 
ferior tubercle  behind  the  symphysis  of  the  mandible,  and 
passes  downwards  and  backwards  to  be  inserted  into  the  front 
of  the  body  of  the  os  hyoides.  This  round  muscle  is  situated  in 
the  mesial  line,  parallel  to  its  fellow.  Its  nerve  comes  from  the 
hypoglossal,  and  its  blood  from  the  lingual  artery.  Its  action  is 
to  draw  the  os  hyoides  forwards  and  upwards  ;  and,  if  the  hyoid 
bone  be  fixed,  it  depresses  the  mandible. 


HYO-GLOSSUS. 


117 


Hyo-glossus. — The  hyo-glossus  arises  from  the  body,  the 
greater  and  lesser  cornua  of  the  os  hyoides,  and  is  inserted  into 
the  posterior  two-thirds  of  the  side  of  the  tongue,  its  fibres 
blending  with  the  stylo-glossus  and  palato-glossus.  It  is  a 
square  and  fiat  muscle,  and  its  fibres  ascend  nearly  perpendicu- 
larly from  origin  to  insertion.  The  fibres  arising  from  the 
body  of  the  hyoid  bone,  termed  the  basio-glossiis,  are  directed 
backwards  and  upwards,  and  overlap  the  fibres  which  have  their 
origin  from  the  greater  cornu  and  are  termed  the  kerato-glossns. 
Those  that  arise  from  the  lesser  cornu  are  termed  the  chondro- 


Styloid 
process. 


Glosso- 
pharyngeal n. 

Hypoglossal  n. 
Occipital  a 

Submandibular 
ganglion. 
Duct  of  sub- 
mandibular 
gland. 
Middle  con- 
strictor m. 

Lingual  a. 

Descendens 
hypoglossi  n. 


^  Chorda  tympani  n. 
i  Gustatory  n. 


Fig.  45.  —  Muscles,  Vessels,  and  Nerves  of  the  Tongue, 


glossHs.  The  nerve  to  the  hyo-glossus  comes  from  the  hypo- 
glossal, and  its  blood  from  the  lingual.  Its  action  (with  that  of 
its  fellow)  is  to  depress  the  tongue.  Observe  the  objects  which 
lie  upon  the  hyo-glossus  ;  namely,  the  hypoglossal  and  gustatory 
nerves  (which  at  the  anterior  border  form  one  or  more  loops  of 
communication  with  one  another),  the  chorda  tympani  nerve, 
the  submandibular  ganglion,  the  submandibular  gland  and  its 
duct,  the  hyoid  branch  of  lingual  artery,  the  lingual  vein,  the 
sublingual  gland,  the  digastric,  stylo-hyoid,  stylo-glossus,  and 
mylo-hyoid  muscles.  Beneath  the  hyo-glossus  muscle  lie 
the  lingual  artery  and  vein,  part  of  the  middle  constrictor  of 


I  I  8  HYPOGLOSSAL    NERVE. 

the  pharynx,  part  of  the  genio-hyo-glossus,   the  linguahs,   and 
the   glosso-pharyngeal  nerve. 

Genio-hyo-glossus.  —  The  genio-hyo-glossus  arises  by  a 
tendon  from  the  upper  tubercle  behind  the  symphysis  of  the 
mandible,  and  is  inserted  as  follows  :  the  lower  fibres  into  the 
body  of  the  os  hyoides ;  the  upper  fibres  into  the  tongue  from 
the  base  to  the  apex.  It  is  the  largest  and  most  important  of 
the  muscles  of  the  tongue.  It  is  fan-shaped,  with  the  apex 
attached  to  the  symphysis  ;  thence  its  fibres  radiate  into  the 
entire  length  of  the  tongue.  Externally,  the  muscle  is  in  relation 
with  the  stylo-glossus,  lingualis,  and  hyo-glossus,  the  lingual 
artery,  the  sublingual  gland,  Wharton's  duct,  the  hypoglossal 
and  gustatory  nerves  ;  ijiferiorly,  by  its  lower  border  it  is  in  con- 
tact with  the  genio-hyoid  ;  above,  by  its  anterior  border,  with  the 
mucous  membrane  of  the  mouth  ;  and  internally,  it  is  in  contact 
with  its  fellow  and  the  fibrous  septum  of  the  tongue.  It  derives 
its  nerves  from  the  hypoglossal,  and  its  blood  from  the  lingual 
artery.  Its  action  is  various.  The  posterior  fibres,  by  raising 
the  OS  hyoides  and  drawing  forwards- the  base  of  the  tongue, 
protrude  the  tongue  out  of  the  mouth  ;  the  anterior  draw  the 
tongue  back  again.  When  every  part  of  the  muscle  acts,  it 
draws  down  the  whole  tongue,  and  is  therefore  one  of  the  chief 
muscles  concerned  in  suction. 

Stylo-glossus.  —  The  stylo-glossus,  a  long  and  slender 
muscle,  arises  from  the  outer  side  of  the  styloid  process  near 
its  apex  and  from  the  stylo-mandibular  ligament  ;  its  fibres  pass 
downwards  and  forwards,  and  then  nearly  horizontal,  and  are 
ijiserted  along  the  side  of  the  tongue.  It  runs  outside  the  hyo- 
glos.sus  nearly  to  the  tip  of  the  tongue,  and  blends  with  the 
fibres  of  this  muscle,  as  well  as  with  the  palato-glossus.  Its 
nerve  comes  from  the  hypoglossal.  Its  action  is  to  retract  the 
tongue. 

Hypoglossal  Nerve.  —  The  hypoglossal,  or  twelfth  cranial 
nerve,  is  the  motor  nerve  of  the  muscles  of  the  tongue.  It 
arises  by  several  filaments,  twelve  to  fifteen,  from  the  front  of 
the  medulla  between  the  anterior  pyramid  and  the  olivary  body. 
It  pierces  the  dura  in  two  fasciculi  which  leave  the  skull  through 
the  anterior  condylar  foramen  ;  these  subsequently  blend  to  form 
a  single  nerve  trunk.  It  lies  deeply  beneath  the  internal  jugular 
vein  and  internal  carotid  artery,  where  it  is  intimately  connected 
with  the  lower  ganglion  of  the  pncumogastric  nerve  ;  it  then 
comes  up  between  the  artery  and  vein,  and,  immediately  below 


SUBLINGUAL    GLAND.  I  I9 

the  posterior  belly  of  the  digastric,  curves  forwards  over  the 
occipital,  the  internal  and  external  carotid,  and  facial  arteries. 
Next  it  crosses  the  hyo-glossus  muscle,  and  passing  beneath  the 
mylo-hyoid,  divides  into  branches  which  supply  the  following 
muscles ;  namely,  the  stylo-glossus,  hyo-glossus,  genio-hyo-glos- 
sus,  lingualis,  and  the  genio-hyoideus. 

As  it  curves  round  the  occipital  artery,  the  hypoglossal  nerve 
sends  the  desccndens  Jiypoglossi  to  the  depressors  of  the  os 
hyoides  (p.  117).  It  also  sends  a  nerve  to  the  thyro-hyoideus, 
which  proceeds  from  it  where  it  crosses  over  the  external  caro- 
tid, accompanied  by  the  hyoid  branch  of  the  lingual  artery. 
Near  the  anterior  border  of  the  hyo-glossus  it  communicates  by 
several  loops  with  the  gustatory  nerve.     (Fig.  45,  p.  117.) 

The  hypoglossal  at  its  origin  is  purely  a  motor  nerve.  But 
after  leaving  the  skull,  it  receives  communications  from  the  first 
two  cervical  nerves.  These  communications  are  important 
physiologically  for  two  reasons  :  i.  They  account  for  the  hypo- 
glossal nerve  containing  sensory  fibres.  2.  They  contribute 
the  greater  part  of  the  filaments  of  the  descendens  hypoglossi. 
It  is  also  connected  by  small  branches  with  the  pneumogastric 
nerve  and  the  superior  cervical  ganglion  of  the  sympathetic  at 
the  base  of  the  skull. 

Sublingual  Gland.  —  The  sublingual  gland  lies  immediately 
beneath  the  mucous  membrane  of  the  floor  of  the  mouth.  Its 
shape  is  oblong,  with  the  long  axis  (about  an  inch  and  a  half, 
^.6  cm)  directed  from  before  backwards,  and  it  weighs  45  grains 
{3 gm.)  ;  its  wolixvae.  is  2.^  c.cm.  Its  relations  are  as  follows: 
above,  it  is  covered  with  mucous  membrane  ;  beloiv,  it  rests  upon 
the  upper  surface  of  the  mylo-hyoid  muscle  ;  internally,  it  is  in 
contact  with  the  hyo-glossus,  genio-hyo-glossus,  stylo-glossus, 
the  gustatory  nerve,  and  Wharton's  duct  —  its  length  is  i^. 
inches  {3.8  cm.),  breadth  -jV  of  an  inch  (2  mm.);  posteriorly,  with 
the  submandibular  gland  ;  and  in  front,  it  rests  in  a  depression 
behind  the  symphysis  of  the  mandible. 

The  ducts  of  the  sublingual  gland  (ducts  of  Rivinus)  vary  in 
number  from  eight  to  twenty.  They  terminate  by  minute 
openings  behind  the  orifice  of  the  submandibular  duct,  along 
the  ridge  felt  upon  the  floor  of  the  mouth.  One  or  more  ducts 
terminate  in  the  submandibular  duct  ;  one  of  these  takes  the 
name  of  the  d?tct  of  BartJiolin.  Its  length  is  a  little  more  than 
I  of  an  inch  {20  mm),  breadth  2V  of  an  inch  (/  mm). 

The  duct  of  the  submandibular  gland   may  now  be  traced 


I20  SUBMAXILLARY    OR    SUBMANDIBULAR    GANGLION. 

across  the  hyo-glossus,  and  under  the  gustatory  nerve  to  the 
floor  of  the  mouth. 

Lingual  or  Gustatory  Nerve.  —  This  nerve  is  a  branch  of 
the  mandibular  or  third  division  of  the  fifth  pair  of  cranial 
nerves.  Emerging  beneath  the  external  pterygoid  muscle,  in 
company  with,  but  in  front  of,  the  inferior  dental  nerve,  it  rests 
upon  the  internal  pterygoid  muscle.  It  descends  between  this 
latter  muscle  and  the  ramus  of  the  mandible,  and  curves  forwards 
towards  the  side  of  the  tongue  over  the  superior  constrictor  of 
the  pharynx,  along  the  upper  part  of  the  hyo-glossus,  at  the 
anterior  border  of  which  it  crosses,  superficially,  the  duct  of 
the  submandibular  gland  (Fig.  44,  p.  114).  Having  reached 
the  under  part  of  the  tongue,  the  nerve  divides  into  numerous 
branches  which  pierce  the  muscular  structure  of  the  tongue, 
and  then  break  up  into  filaments  which  supply  the  mucous 
membrane  and  the  fungiform  and  filiform  papillae  on  its  anterior 
three-fourths.  Beneath  the  external  pterygoid  it  is  joined  at 
an  acute  angle  by  the  chorda  tympani,  a  branch  of  the  facial 
nerve;  in  its  course  it  gives  off  some  communicating  branches 
to  the  hypoglossal  nerve  near  the  anterior  border  of  the  hyo- 
glossus.  It  supplies  also  the  mucous  membrane  of  the  mouth, 
gums,  and  the  sublingual  gland,  one  or  more  branches  to  the 
submandibular  ganglion,  and  at  the  apex  of  the  tongue  the 
terminal  branches  of  this  nerve  and  the  hypoglossal  are  con- 
nected. 

Submaxillary  or  Submandibular  Ganglion.  —  At  the 
lower  border  of  the  gustatory  nerve  as  it  lies  upon  the  hyo- 
glossus  muscle,  and  before  it  crosses  the  submandibular  duct, 
you  will  find  a  small,  convex,  triangular  ganglion,  about  the  size 
of  a  pin's  head.  Like  the  other  ganglia  in  connection  with  the 
branches  of  the  fifth  pair,  it  receives  filaments  of  communication 
of  three  different  kinds  —  viz.,  motor,  sensory,  and  sympathetic. 
Its  motor  root  is  the  chorda  tympani,  derived  from  the  facial 
nerve  ;  its  sensory  branches  proceed  from  the  gustatory  ;  and  its 
connection  with  the  sympathetic  system  is  established  by  a 
branch  which  comes  from  the  ncrvi  molles  or  8th  n.  round  the 
facial  artery.  The  ganglion  supplies  five  or  six  branches  of 
distribution  to  the  submandibular  gland,  its  duct,  and  the  mu- 
cous membrane  of  the  floor  of  the  mouth.  Meckel  describes  a 
small  branch  of  the  ganglion  which  sometimes  passes  forwards 
to  join  a  branch  of  the  hypoglossal,  on  the  hyo-glossus  m.,  and 
ends  in  the  genio-hyo-glossus. 


LINGUAL    ARTERY.  121 

Lingual  Artery.  —  The  lingual  artery  is  generally  the  sec- 
ond branch  of  the  external  carotid.  Curving  slightly  upwards 
and  inwards  from  its  origin,  the  artery  soon  runs  forwards 
round  the  great  cornu  of  the  hyoid  bone,  beneath  the  posterior 
belly  of  the  digastric  and  stylo-hyoideus,  and  then  passes 
beneath  the  hyo-glossus  m.  parallel  to  the  os  hyoides.  At  the 
anterior  edge  of  the  hyo-glossus  it  ascends  to  the  under  surface 
of  the  tongue,  and  is  continued  forwards  to  the  apex  of  the 
tongue  under  the  name  of  ranine.  Before  the  artery  passes 
beneath  the  hyo-glossus,  it  is  crossed  by  the  hypoglossal  nerve, 
but  it  immediately  after  becomes  separated  from  the  nerve  by 
this  muscle.  Under  the  hyo-glossus  the  artery  lies  upon  the 
middle  constrictor  of  the  pharynx  and  the  genio-hyo-glossus  ; 
in  the  substance  of  the  tongue  it  lies  between  the  genio-hyo- 
glossus  and  the  inferior  lingualis.  The  curves  made  by  the 
artery  are  for  the  purpose  of  allowing  the  elongation  of  the 
tongue.     Its  branches  are  (Fig.  43,  p.  113):  — 

1.  The  hyoid,  a  small  artery  which  runs  along  the  upper  border  of  the  hyoid 
bone,  supplying  the  muscles  and  anastomosing  with  its  fellow,  and  with  the  hyoid 
branch  of  the  superior  thyroid  artery.  The  nerve  to  the  thyrohyoid  muscle,  which 
is  derived  from  the  hypoglossal,  accompanies  this  artery. 

2.  The  dorsales  lingius,  two  or  more,  run  under  the  hyo  glossus  to  the  back  of 
the  tongue,  the  mucous  membrane,  tonsil,  and  soft  palate. 

3.  The  s^tblingiial,  arising  near  the  anterior  border  of  the  hyo-glossus,  supplies 
the  sublingual  gland,  the  mylo-hyoideus,  and  the  mucous  membrane  of  the  mouth 
and  gums.  This  artery  generally  gives  off  the  little  artery  of  the  fra;num  linguae, 
which  is  sometimes  wounded  in  cutting  the  frnsnum  in  children  who  are  tongue- 
tied,  especially  when  we  neglect  the  rule  of  pointing  the  scissors  downwards  and 
backwards. 

4.  The  ranine  is  the  termination  of  the  lingual  artery.  As  it  runs  forwards  to 
the  tip  of  the  tongue  along  the  outer  side  of  the  genio-hyo-glossus,  along  with  the 
gustatory  nerve,  it  distributes  branches  to  the  tongue,  and  at  the  tip  inosculates 
slightly  with  its  fellow  of  the  opposite  side. 

The  ranine  vein,  commencing  at  the  tip  of  the  tongue,  after 
joining  with  the  venae  comites  of  the  lingual  artery  and  the 
dorsal  veins  of  the  tongue,  runs  along  its  under  surface  over 
the  hyo-glossus,  and  terminates  in  the  internal  jugular  or  facial 
vein. 

The  best  place  for  finding  and  tying  the  lingual  artery  has 
been  mentioned  (p.  116).  The  rule  laid  down  is  trustworthy 
only  when  the  artery  runs  its  normal  course.  We  have  known 
an  instance  in  which  a  good  anatomist  failed  in  an  attempt  to 
tie  the  lingual  artery,  because  the  vessel  arose  from  the  facial 
behind  the  submandibular  gland,  and  then  passed  through  the 
mylo-hyoideus  to  reach  the  tongue. 


122  POSTERIOR    AURICULAR    ARTERY. 

Occipital  Artery, — The  occipital  artery  arises  from  the 
posterior  part  of  the  external  carotid,  usually  opposite  the  facial 
artery,  and  runs  upwards  and  backwards  along  the  lower  border 
of  the  digastric  towards  the  mastoid  process.  It  passes  then 
under  the  posterior  belly  of  the  digastric,  and  further  on  in 
its  course  it  lies  in  the  interval  between  the  transverse  process 
of  the  atlas  and  the  mastoid  process,  close  to  the  rectus  capitis 
lateralis;  it  now  changes  its  direction,  for  it  runs  horizontally 
backwards  in  the  occipital  groove  of  the  temporal  bone,  under 
all  the  muscles  attached  to  the  mastoid  process  —  namely,  the 
sterno-mastoid,  the  splenius  capitis,  the  trachelo-mastoid,  and 
the  digastric,  and  it  lies  on  the  sujferior  oblique  and  the  com- 
plexus.  Arrived  at  the  back  of  the  head,  the  artery  pierces  the 
cranial  attachment  of  the  trapezius,  and  ascending,  divides  into 
wide-spreading  branches  for  the  supply  of  the  scalp. 

In  the  first  part  of  its  course,  the  occipital  artery  crosses  over 
the  internal  carotid  artery,  the  internal  jugular  vein,  the  pneu- 
mogastric  and  the  spinal  accessory  nerves,  and  is  itself  crossed 
by  the  hypoglossal  nerve.  It  sends  off  the  seven  following 
branches : — 

1.  ATuscular  branches  to  the  digastric,  stylo-hyoid,  splenius,  and  trachelo- 
mastoid  muscles. 

2.  The  superior  ste7-no-7nastoid,  which  enters  the  muscles  with  the  nervus 
accessorius. 

3.  The  auricular  ramifies  on  the  cranial  aspect  of  the  concha. 

4.  Thfi posterior  tneniiigeal  ascends  with  the  internal  jugular  vein,  and  enters 
the  cranium  through  the  foramen  jugulare  to  supply  the  dura  of  the  posterior 
fossa. 

5.  The /r/;/(r(?/j  f^rz'/cw,  which  we  shall  see  better  hereafter,  is  a  short  trunk 
which  runs  down  the  back  of  the  neck,  and  divides  into  two  branches  —  a  super- 
ficial, lying  beneath  the  splenius,  and  supplying  also  the  trapezius,  and  a  deep 
branch  lying  under  the  comple.xus,  and  anastomosing  with  branches  of  the  vertebral 
and  with  the  deep  cervical  branch  of  the  superior  intercostal  artery  between  this 
muscle  and  the  semi-spinalis  colli. 

6.  The  mastoid  enters  the  foramen  in  the  mastoid  process,  and  supplies  the 
dura. 

7.  The  cranial  branches  supply  the  scalp  on  its  posterior  aspect,  and  anasto- 
mose freely  with  the  corresponding  artery  of  the  opposite  side,  the  posterior 
auricular  and  the  supei-ficial  temporal  arteries. 

The  occipital  vciji  accompanies  the  artery,  and  is  connected 
with  the  lateral  sinus  through  a  small  vein  running  through  the 
mastoid  foramen.  It  subsequently  terminates  in  the  internal 
jugular,  occasionally  in  the  external  jugular  vein. 

Posterior  Auricular  Artery.  —  The  posterior  auricular 
artery  (Mg.  43,  p.  113),  the  fifth  Isranch,  is  given  off  from  the 
posterior  part  of  the  external  carotid.     It  arises  above  the  di- 


ASCENDING    PHARYNGEAL    ARTERY.  I  23 

gastric,  lies  on  the  styloid  process,  and  under  cover  of  the 
parotid  gland  reaches  the  furrow  between  the  cartilage  of  the 
ear  and  the  mastoid  process.  Before  it  reaches  the  furrow  it  is 
crossed  by  the  facial  nerve,*  and  just  beneath  it  is  the  spinal 
accessory.  Above  the  mastoid  process  it  divides  into  two 
branches,  a  posterior  inosculating  with  the  occipital,  and  an 
anterior  communicating  with  the  temporal.  It  supplies  the 
back  of  the  scalp  and  the  cartilage  of  the  ear.     It  gives  off  — 

1.  Small  branches  of  the  digastric,  stylo  hyold,  and  the  parotid  gland. 

2.  The  stylo-mastoidy  a  very  constant  little  artery,  which  runs  through  the  stylo- 
mastoid foramen  to  supply  the  mastoid  cells,  the  vestil:)ule,  and  the  membrana 
tympani.  In  young  subjects,  one  of  *hese  latter  branches  forms  a  vascular  circle 
around  the  circumference  of  the  membrane  with  the  tympanic  branch  of  the  in- 
ternal maxillary. 

3.  The  auricular  branch  runs  along  lie  cranial  surface  of  the  auricle,  and 
anastomoses  with  the  superficial  temporal  and  occipital  arteries.  Some  of  the 
branches  pierce  the  cartilage  of  the  ear  and  ramify  on  its  anterior  surface. 

4.  The  mastoid  branch  is  distributed  to  the  structures  over  the  mastoid 
process. 

The  posterior  auricular  vein  is  rather  large,  and  running  over 
the  mastoid  process,  terminates  in  the  external  jugular  vein. 

Posterior  Auricular  Nerve.  —  The  posterior  auricular 
nerve  lies  close  to  the  artery  of  the  same  name.  It  is  the  first 
branch  of  the  seventh  or  facial  nerve  after  its  exit  from  the 
stylo-mastoid  foramen.  It  runs  behind  the  ear  and  divides  into 
an  auricular  branch  to  the  retrahens  and  the  attollens  aurem, 
and  an  occipital  branch  to  the  posterior  belly  of  the  occipito- 
frontalis,  which  communicates  with  the  small  occipital  nerve. 
The  nerve  is  connected  with  the  great  auricular  nerve  of  the 
cervical  plexus,  and  with  the  auricular  branch  of  the  pneumo- 
gastric  nerve. 

Ascending  Pharyngeal  Artery. — This  long  and  straight 
branch  arises  about  half  an  inch  above  the  division  of  the  com- 
mon carotid  (Fig.  43,  p.  113).  It  ascends  between  the  internal 
carotid  and  the  side  of  the  pharynx  to  the  base  of  the  skull, 
lying  upon  the  rectus  capitis  anticus  major.  It  gives  off 
numerous  branches  ;  among  them  are  — 

1.  Small  external  branches  \s\\\c\\  pass  outwards  to  supply  the  anterior  recti- 
muscles,  the  superior  cervical  ganglion,  the  pneumogastric  and  hypoglossal  nerves, 
and  the  prevertebral  lymphatic  glands.  They  anastomose  with  the  ascending  cer- 
vical artery. 

2.  Pharyngeal  branches,  some  of  which  pass  to  the  two  lower  pharyngeal  con- 
strictors  and   the    stylo-pharyngeus ;  one,  the  largest   of  all,  enters   the  pharynx 

*  The  posterior  auricular  artery  frequently  runs  superficial  to  the  facial  nerve. 


124  CERVICAL    PLEXUS    OF    NERVES. 

above  the  superior  constrictor,  and  terminates  in  the  soft  palate,  the  Eustachian 
tube,  and  the  tonsils. 

3.  Meiiiiigi-al  or  diiral  branches  ;  one  passes  through  the  foramen  lacenim  pos- 
ticum,  with  the  internal  jugular  vein,  and  is  distributed  to  the  dura  of  the  occipital 
fossa ;  another  through  the  foramen  lacerum  medium,  and  one  through  the  anterior 
condylar  foramen. 

The  p]iaryngeal  vein  receives  some  dural  branches,  also 
small  veins  from  the  soft  palate,  Eustachian  tube,  and,  uniting, 
form  the  pharyngeal  plexus  which  opens  into  the  internal  jug- 
ular or  common  facial  vein. 

The  examination  of  the  two  remaining  branches  of  the  ex- 
ternal carotid,  the  internal  maxillary  and  temporal,  must  for  the 
present  be  postponed.  Meanwhile  the  student  should  make 
out  the  deep  cervical  plexus  and  its  branches. 

Cervical  Plexus  of  Nerves.  —  This  plexus  is  formed  by 
the  anterior  branches  of  the  four  upper  cervical  nerves.  It  con- 
sists of  a  series  of  loop-like  communications,  between  these 
nen'-es,  close  to  the  transverse  processes  of  the  four  upper  cer- 
vical vertebrae  ;  each  nerve  dividing  into  an  ascending  and  a 
descending  branch,  with  the  exception  of  the  first.  The  plexus 
rests  on  the  levator  anguli  scapulae  and  scalenus  medius,  and  is 
situated  behind  the  sterno-mastoid  m.  and  the  internal  jugular 
vein. 

The  plexus  gives  off  superficial  and  deep  branches,  the  super- 
ficial coming  from  the  second,  third,  and  fourth  nerves,  the  deep 
from  the  third  and  fourth  n.  The  superficial  branches  have 
been  already  described  (p.  81). 

The  deep  branches  may  be  divided  into  an  internal  and  an 
external  series. 

Internal  Series.  —  i.  The  phrenic  arises  from  the  third, 
fourth,  and  fifth  cervical  nerves,  descends  obliquely  inwards 
over  the  scalenus  anticus,  and  then  crosses  over  the  first  part  of 
the  subclavian  artery.  Near  the  thorax  it  is  joined  by  the  sym- 
pathetic, and  frequently  by  a  looped  branch  from  the  nerve  to 
the  subclavius  muscle.  Its  course  through  the  thorax  to  its 
destination  in  the  diaphragm  will  be  described  on  p.  127. 

2.  The  commiinic antes  Jiypoglossi  come  from  the  second  and 
third  cervical  nerves,  wind  round  the  internal  jugular  vein,  and 
join  the  descendens  hypoglossi  in  front  of  the  carotid  sheath, 
forming  the  "ansa  hypoglossi."  They  supply  the  depressor 
muscles  of  the  os  hyoides  and  larynx. 

3.  Muscular  branches  which  proceed  from  the  first  cervical 
and  the  loop  between  it  and  the  second  cervical,  to  the  recti 
antici,  the  rectus  lateralis,  and  longus  colli  muscles. 


SCALENUS    POSTICUS.  125 

4.  Branches  which  communicate  with  the  pneumogastric, 
hypoglossal,  and  sympathetic  nerves,  and  one  to  join  the  fifth 
cervical. 

External  Series.  —  i.  One  or  more  communicating 
branches  to  the  nervus  accessorius  :  firstly  in  the  sterno-mastoid, 
then  in  the  occipital  triangle,  and  lastly  beneath  the  trapezius. 

2.  Muscular  brandies  to  supply  the  trapezius,  levator  anguli 
scapulae,  scalenus  medius,  and  sterno-mastoid.  The  branches 
to  the  trapezius,  levator  anguli  scapulae,  and  scalenus  medius, 
come  from  the  third  and  fourth  ;  the  branch  to  the  sterno- 
mastoid  from  the  second  cervical  nerve. 

Dissection.  —  The  clavicle  should  now  be  sawn  through  the 
middle,  and  the  sternal  half  raised  with  the  sterno-mastoid 
attached,  so  that  the  bone  can  be  replaced,  to  study  its  relation 
to  the  subjacent  parts.  The  scalene  muscles  and  the  sub-cla- 
vian  artery  throughout  its  whole  course  must  next  be  care- 
fully dissected.  While  this  is  being  done,  the  student  must  be 
careful  not  to  injure  the  branches  of  the  subclavian  artery,  the 
lymphatic  duct  on  the  right,  and  the  thoracic  duct  on  the  left 
side,  the  nerve  to  the  subclavius  m.,  the  phrenic  nerve,  the  cer- 
vical and  the  brachial  plexuses  of  nerves,  and  their  small  branches. 

Scalene  Muscles.  —  The  scalene  muscles,  so  called  from 
their  resemblance  to  a  scalene  triangle,  extend  from  the  trans- 
verse processes  of  the  cervical  vertebrae  to  the  first  and  second 
ribs.  They  may  be  considered  as  intercostal  muscles,  since 
the  transverse  processes  of  the  cervical  vertebrae  are  but  rudi- 
mentary ribs.  Anatomists  describe  them  as  three  separate  mus- 
cles —  an  anterior,  a  middle,  and  a  posterior ;  the  anterior  and 
middle  are  attached  to  the  first  rib,  the  posterior  to  the  second. 
In  plan  and  purpose  these  three  muscles  are  one. 

Scalenus  Anticus.  —  The  scalenus  anticus  is  attached  above 
to  the  anterior  tubercles  of  the  transverse  processes  of  the  third, 
fourth,  fifth,  and  sixth  cervical  vertebrae,  and  below  by  a  flat 
tendon  to  the  tubercle  on  the  imier  border  and  upper  surface  of 
the  first  rib  in  the  front  of  the  groove  for  the  subclavian  artery. 

Scalenus  Medius. —  The  scalenus  medius  is  attached  above 
to  the  posterior  tubercles  of  the  transverse  processes  of  all  the 
cervical  vertebrae  except  the  first,  and  below  to  the  first  rib  be- 
hind the  scalenus  anticus,  extending,  from  the  tubercle,  forwards 
for  an  inch  and  a  half. 

Scalenus  Posticus.  — -The  scalenus  posticus  is  attached  above 
to  the  posterior  tubercles  of  the  transverse  processes  of  the  two 


126 


RELATIONS    OF    SCALENUS    ANTICUS    MUSCLE. 


or  three  lowest  cervical  vertebras,  and  below  to  the  second  rib 
between  its  tubercle  and  angle,  anterior  to  the  levator  costce,  and 
behind  the  serratus  magnus. 

Nerve-supply  to  Scalene  Muscles. — The  scaleni  are  sup- 
plied by  branches  derived  from  the  lower  cervical  nerves. 

Action  of  Scalene  Muscles. — The  scalene  muscles  are  im- 
portant agents  in  raising  the  thorax,  in  a  deep  inspiration.  Take 
a  deep  breath,  and  you  can  easily  feel  them  contracting.  They 
can  bend  the  cervical  portion  of  the  spine,  if  their  lower  attach- 
ment be  the  fixed  point,  as  in  rising  from  the  recumbent  position. 

Relations  of  Scalenus  Amicus  Muscle. — The  scalenus  an- 


FlG.  46. SCAIENE    MUSCI-ES, 

19.   Scalenus  anticus  muscle.     20,20.    Scalenii  medius  and  posticus.     21,21.    Fasciculi  of  the  leva- 
tor anguli  scapula;  inu.scle.     22.    Splenius  capitis  musclu.     23.    Splenius  colli  muscle. 

ticus  is  one  of  those  muscles  about  which  we  ought  to  know 
well  all  that  lies  in  front  of  it,  and  all  that  lies  behind  it.  In 
the  front  of  it  are :  the  clavicle,  the  subclavius,  the  clavicular 
origin  of  the  sterno-mastoid,  the  omo-hyoid,  the  phrenic  nerve, 
the  subclavian  vein,  the  .supra-scapular,  the  posterior  scapular, 
and  the  ascending  cervical  arteries.  Behind  it  are  the  sub- 
clavian artery,  the  five  nerves  which  form  the  brachial  plexus, 
and  the  pleura  ;  to  its  inner  side  is  the  internal  jugular  vein, 
and  the  vertebral  artery  separates  it  from  the  longus  colli. 


RIGHT    SUBCLAVIAN    ARTERY.  12/ 

Make  your  finger  familiar  with  the  feel  of  the  tubercle  on  the 
first  rib,  to  which  the  scalenus  anticus  is  attached.  This  tuber- 
cle is  the  guide  to  the  subclavian  artery,  for  it  enables  you  to 
find  the  outer  edge  of  the  scalenus  anticus,  where  you  must  look 
for  the  vessel.  Is  the  scalenus  anticus  entirely  concealed  from 
view  by  the  sterno-mastoid,  or  not  .'*  This  will  depend  upon  the 
breadth  of  the  clavicular  attachment  of  the  sterno-mastoid.  As 
a  general  rule,  it  may  be  said  that  the  scalene  muscle  is  con- 
cealed by  the  sterno-mastoid,  and  that  consequently,  in  tying 
the  subclavian  artery,  it  may  be  necessary  to  divide  partially  the 
clavicular  origin  of  the  muscle. 

Phrenic  Nerve.  —  The  phrenic  nerve  runs  down  in  front  of 
the  scalenus  anticus,  from  the  outer  to  the  inner  border.  It 
arises  from  the  third,  fourth,  and  fifth  cervical  nerves,  but 
chiefly  from  the  fourth.  It  enters  the  chest  between  the  sub- 
clavian artery  and  vein,  crosses  in  front  of  the  internal  mam- 
mary artery,  and  continues  its  course  between  the  pericardium 
and  pleura,  in  front  of  the  root  of  the  lung,  to  the  diaphragm, 
which  it  supplies. 

When  the  spinal  cord  is  injured  above  the  fourth  cervical 
vertebra,  the  origin  of  the  phrenic  is  implicated  ;  therefore,  the 
diaphragm,  as  well  as  the  other  muscles  of  inspiration,  are  par- 
alyzed.    Death  is  the  immediate  result.* 


COURSE  AND  RELATIONS  OF  THE  SUBCLAVIAN 

ARTERIES. 

The  left  subclavian  artery  differs  from  the  right,  not  only  in 
its  origin,  but  in  the  relations  of  the  first  part  of  its  course. 
The  right  should,  therefore,  be  examined  first,  and  then  the 
differences  between  it  and  the  left. 

Right  Subclavian  Artery. — The  right  subclavian  artery  is 
one  of  the  two  great  branches  into  which  the  arteria  innominata 

*  The  phrenic  nerve  is  joined  by  a  filament  from  the  sympathetic,  and  fre- 
quently by  a  filament  from  that  branch  of  the  brachial  plexus  which  supplies  the 
subclavius  muscle.  This  is  sometimes  a  branch  of  considerable  size,  and  forms 
the  greater  portion  of  the  phrenic  itself.  We  have  met  with  many  instances  in 
which  thfs  accessory  branch  was  larger  than  the  regular  trunk ;  in  all  of  them  it 
crossed  over  the  subclavian  artery  in  the  third  part  of  its  course,  and  would  prob- 
ably have  been  injured  in  the  operation  of  tying  this  vessel.  That  such  an  acci- 
dent has  actually  happened  is  reported  by  Bransby  Cooper  in  his  surgical  lectures. 
He  speaks  of  having  injured  this  accessory  brancli  of  the  phrenic  in  tying  the  sub- 
clavian artery.     The  patient  had  incessant  spasm  of  the  diaphragm  till  he  died. 


128  RIGHT    SUBCLAVIAN    ARTERY. 

divides  behind  the  sterno-clavicular  joint.  It  runs  outwards 
behind  the  scalenus  anticus,  then  incUnes  downwards  over  the 
first  rib,  at  the  outer  border  of  which  it  takes  the  name  of 
axillary.  The  artery  describes  a  curve,  of  which  the  greatest 
convexity  is  between  the  scalene  muscles.  The  height  to  which 
the  arch  ascends  varies.  Generally,  it  rises  higher  in  women 
than  in  men,  on  the  right  side  than  on  the  left. 

To  study  its  relations  more  precisely,  the  course  of  the  sub- 
clavian is  divided  into  three  parts:  i.  The  part  which  inter- 
venes between  its  origin  and  the  inner  border  of  the  scalenus 
anticus.  2.  That  which  lies  behind  this  scalenus.  3.  That 
which  intervenes  between  the  outer,  border  of  this  scalenus  and 
the  outer  border  of  the  first  rib. 

T\\&  first  portion  of  the  artery  lies  deeply  in  the  neck  and 
passes  upwards  and  outwards  the  inner  border  of  the  scalenus 
anticus.  It  is  covered  by  the  skin,  platysma,  superficial  and 
deep  fasciae,  the  sternal  end  of  the  clavicle,  the  sterno-mastoid, 
sterno-hyoid,  and  sterno-thyroid  muscles,  and  a  layer  of  deep 
fascia,  continued  from  the  inner  border  of  the  scalenus  anticus. 
It  is  crossed  by  the  internal  jugular  and  vertebral  veins,  by  the 
pneumogastric  and  phrenic  nerves,  and  by  some  cardiac  fila- 
ments of  the  sympathetic.  Inferiorly  it  rests  upon  the  pleura. 
BeJiind  the  artery  are  the  recurrent  branch  of  the  pneumo- 
gastric, the  sympathetic  nerve,  the  longus  colli,  the  transverse 
process  of  the  seventh  cervical  vertebra,  and  the  apex  of  the 
lung  covered  with  the  pleura.  The  subclavian  vein  lies  below 
the  artery.  Three  branches  arise  from  this  portion  of  the 
subclavian  —  viz.,  the  vertebral,  internal  mammary,  and  thyroid 
axis. 

In  the  seco7id  (the  highest)  part  of  its  course,  the  artery  lies 
between  the  scalenus  anticus  and  medius  muscles.  It  is  covered 
by  the  skin,  platysma,  and  superficial  fascia,  by  the  clavicular 
origin  of  the  sterno-mastoid,  the  deep  cervical  fascia,  and  by  the 
scalenus  anticus  and  phrenic  nerve,  which  separate  it  from  the 
subclavian  vein.  Behind  the  artery  is  the  scalenus  medius ; 
above  it,  is  the  brachial  plexus  ;  belozv  it,  is  the  pleura.  Only 
one  branch,  the  superior  intercostal,  is  given  off  from  this  part 
of  the  artery. 

In  the  third  part  of  its  course,  the  artery  passes  downwards 
and  outwards,  and  lies  in  the  supra-clavicular  triangle  upon  the 
surface  of  the  first  rib.  Here  it  is  most  superficial,  and  is 
covered  by  the  skin,  platysma,  the  two  layers  of  the  cervical 


RIGHT    SUBCLAVIAN    ARTERY. 


129 


fascia,  and  the  clavicular  branches  of  the  superficial  cervical 
plexus  ;  subsequently  by  the  supra- scapular  artery  and  vein,  the 
clavicle,  the  subclavias  muscle,  with  its  nerve ;  and,  what  is  of 
much  more  consequence,  it  is  here  crossed  by  the  external  jug- 
ular and  (often)  the  supra  and  posterior  scapular  veins ;  so  that 


jrd  cervical  n. 
4th  cervical  n. 


5th  cervical  n 


Line  of  reflec- 
tion of  peri- 
cardium. 


Cervicalis 
ascendens  a. 

Scalenus  amicus. 
Inferior  thyroid 
artery. 

Superficialis  colli 

a. 
Phrenic  n. 

Posterior 

scapular  a. 
Supra-scapular  a. 
Subclavian  a. 
Superior 

intercostal  a. 
Internal 

mammary  a. 
Pneumogastric  n. 

Phrenic  n 


Appendix  of  left 
auricle. 


Fig.  47- 


there  is  here  a  confluence  of  large  veins  in  front  of  the  artery. 
The  subclavian  vein  is  situated  below  the  artery,  but  on  a  plane 
anterior  to  it.  Beloiv  it,  is  the  first  rib,  and  behind  it  the  sca- 
lenus medius.  Above  the  artery,  and  to  its  outer  side,  are  the 
trunk  nerves  of  the  brachial  plexus  and  the  omo-hyoid  m.  One 
of  these  nerves  (the  conjoined  fifth  and  sixth  cervical)  runs  so 


130  LEFT  SUBCLAVIAN  ARTERY, 

nearly  parallel  with  the  artery,  and  on  a  plane  anterior  to  it,  it  is 
quite  possible  to  mistake  the  nerve  for  the  artery  in  the  opera- 
tion of  tying  the  latter.  We  have  heard  a  hospital  surgeon  of 
great  experience  say  that  he  had  seen  this  mistake  committed 
on  three  separate  occasions.  In  this  part  of  its  course,  the 
artery  as  a  rule  gives  off  no  branches ;  the  most  frequent  excep- 
tions are  the  posterior  scapular  and  supra-scapular. 

Left  Subclavian  Artery.  —  The  left  subclavian  is  the  last 
of  the  three  great  branches  which  arise  from  the  arch  of  the  aorta. 
It  ascends  nearly  vertically  out  of  the  chest,  and  then  arches 
in  front  of  the  apex  of  the  lung  and  pleura  to  reach  the  inner 
border  of  the  scalenus  anticus,  behind  which  it  runs  over  the 
first  rib. 

In  the  first  part  of  its  course  the  left  subclavian  lies  deeply 
in  the  chest  near  the  spine.  On  its  outer  or  left  side  it  is  cov- 
ered by  the  pleura ;  on  its  inner  or  right  side  are  first  the 
trachea,  then  the  oesophagus  and  thoracic  duct  ;  in/;w//are  the 
left  lung,  covered  with  its  pleura,  the  pneumogastric  and  phrenic 
nerves,  and  the  cardiac  branches,  all  of  which  lie  parallel  with 
the  artery,  the  left  common  carotid,  and  the  left  brachio-ceph- 
alic  vein ;  at  the  level  of  the  upper  part  of  the  chest  it  has  in 
front  the  sterno-thyroid,  sterno-hyoid,  the  sterno-mastoid  mus- 
cles, the  left  internal  jugular  and  vertebral  veins,  and  the  sternal 
end  of  the  clavicle  ;  beJiind  it  are  the  longus  colli,  the  vertebral 
column,  the  inferior  cervical  ganglion  of  the  sympathetic,  the 
oesophagus,  and  the  thoracic  duct. 

Behind  the  scalenus  anticus,  and  on  the  surface  of  the  first 
rib,  the  relations  of  the  left  subclavian  are  similar  to  those  of 
the  right  (p.  128). 

The  left  subclavian,  then,  differs  from  the  right  only  in  the 
first  part  of  its  course.     Now,  what  are  these  differences } 

1.  The  left  subclavian  comes  direct  from  the  arch  of  the 
aorta,  and  is  therefore  longer,  deeper  in  the  chest,  and  more 
vertical  than  the  right,  which  comes  from  the  arteria  innom- 
inata. 

2.  The  left  subclavian  is  in  close  relation  with  the  oesopha- 
gus and  the  thoracic  duct :  the  right  is  not. 

3.  The  left  subclavian  is  crossed  by  the  left  brachio-cephalic 
vein. 

4.  The  left  subclavian  has  the  phrenic,  pneumogastric,  and 
cardiac  nerves  nearly  parallel  with  it  ;  on  the  right  side,  these 
nerves  cross  the  artery  at  a  nearly  right  angle. 


LEFT  SUBCLAVIAN  ARTERY. 


131 


5.  The  left  subclavian  is  not  embraced  by  the  recurrent  lar- 
yngeal nerve,  like  the  right  subclavian. 

The  thoracic  duct  bears  an  important  relation  to  the  left  sub- 
clavian. It  ascends  from  the  chest  to  the  left  of  the  oesopha- 
gus and  behind  the  artery  ;  then  arching  behind  the  internal 
jugular  vein  as  high  as  the  seventh  cervical  vertebra,  it  curves 


Fig.  48. — Lymphatic  Vessels  Coming  from  the  Glands  of  the  Neck  and  Axilla. 

I.  Superior  extremity  of  the  thoracic  duct  passing  behind  the  internal  jugular  vein,  in  an  arch. 
2.  Terminal  portion  of  this  arch,  which  enters  in  the  angle  made  by  the  union  of  tlie  internal 
jugular  and  the  subclavian  veins  on  the  left  side. 

downwards  and  forwards  in  front  of  the  scalenus  anticus  to  ter- 
minate in  the  subclavian  vein  at  its  junction  with  the  jugular. 
The  duct  is  so  thin  and  transparent  that  it  easily  escapes  obser- 
vation ;  it  is  most  readily  found  by  raising  the  subclavian  vein 
near  its  junction  with  the  jugular,  and  searching  with  the 
handle  of  the  scalpel  on  the  inner  side  of  the  scalenus  anticus, 
in  front  of  the  vertebral  vein  (Fig.  48). 


132  LEFT  SUBCLAVIAN  ARTERY. 

.  Before  tracing  the  branches  of  the  subclavian  artery,  consider 
some  points  relating  to  the  operation  of  tying  it. 

To  tie  the  artery  in  the  first  part  of  its  course,  namely,  on  the  inner  edge  of 
the  scalenus  anticus,  is  an  operation  of  great  difficulty  and  danger,  even  with  the 
parts  in  a  normal  position.  The  great  depth  at  which  the  artery  is  placed,  the 
size  and  close  proximity  of  its  numerous  branches,  the  large  veins  by  which  it  is 
covered,  its  connection  -with  the  pneumogastric,  recurrent  laryngeal,  phrenic,  and 
sympathetic  nerves,  and,  above  all,  its  close  contiguity  with  the  pleura,  form  a 
combination  of  circumstances  so  formidable  that  one  cannot  be  surprised  the  oper- 
ation has  never  been  performed  wdth  a  favorable  result.  On  the  left  side  the  op- 
eration is  more  difficiJt  to  perform  than  on  the  right,  owing  to  the  difference  in 
the  anatomical  relation  of  the  two  sides. 

In  the  second  part  of  its  course,  between  the  scalene  muscles,  the  artery  is 
more  accessible,  although  it  is  rarely  ligatured  in  this  situation.  It  would  be 
necessary  to  divide  the  clavicular  origin  of  the  sterno-mastoid,  the  cervical  fascia, 
and  the  scalenus  anticus  to  reach  the  vessel ;  the  phrenic  nerve  and  the  subclavian 
vein  would  be  the  chief  objects  exposed  to  injury.  This  operation  was  performed 
first  and  %\ith  success  by  Dupuytren  in  the  year  181 9.  More  recently  it  has  been 
performed  by  Ur.  Warren,  of  Boston.  The  patient  recovered,  though  the  pleura 
was  wounded.* 

But  in  the  last  part  of  its  course,  that  is,  on  the  outer  side  of 
the  scalenus,  the  artery  may  be  tied  with  comparative  facility. 
The  incision  should  be  made  from  three  to  four  inches  (7.5  to 
10  cm.)  in  length,  parallel  with  the  upper  border  of  the  clavicle. 
We  divide  the  platysma,  some  of  the  supra-clavicular  nerves, 
and  the  cervical  fascia.  The  external  jugular  vein  and  its  trib- 
utaries must  be  drawn  to  the  outer  side,  or  divided  and  tied  at 
both  ends. 

The  connective  tissue  should  now  be  carefully  cut  through, 
and  the  posterior  belly  of  the  omo-hyoid  sought  for,  as  it  runs 
just  above  the  clavicle.  After  clearing  away  some  fat  and  cellu- 
lar tissue,  the  outer  border  of  the  scalenus  anticus  must  be  felt 
for,  behind  which  the  artery  will  be  found  lying  upon  the  first 
rib.  The  operator  now  passes  his  finger  downwards  along  the 
outer  border  of  this  muscle,  as  far  as  its  insertion  into  the 
tubercle  of  the  first  rib,  which  can  always  be  distinctly  felt. 
The  artery  having  been  exposed  by  carefully  dividing  a  layer  of 
fascia  immediately  covering  the  vessel,  the  ligature  is  to  be 
passed  round  the  artery  from  above  downwards,  care  being  taken 
not  to  include  in  the  ligature  one  of  the  cords  of  the  brachial 
plexus. 

Mr.  Ramsden,  of  St.  Bartholomew's  Hospital,  was  the  first 
who  tied  the  subclavian  in  the  third  part  of  its  course,  in  the 
year  1 809  ;  since  that  time  the  operation  has  been  repeatedly 
performed,  with  very  favorable  results. 

*  "  Med.  Chirurg.  Trans.,"  vol.  xxix,  p.  25. 


BRANCHES  OF  THE  SUBCLAVIAN  ARTERY. 


133 


In  the  hands  of  a  surgeon  possessed  of  a  practical  knowledge  of  anatomy  the 
operation  is  easy,  provided  all  circumstances  be  favorable;  but  circumstances  are 
often  very  unfavorable.  Anatomical  deviations  are  by  no  means  rare,  and  it  often 
happens  that  the  aneurismal  or  other  tumor,  on  account  of  which  the  operation  is 
performed,  raises  the  clavicle  beyond  its  natural  level,  and  so  cUsturbs  the  parts, 
that  to  expose  the  artery  and  place  a  ligature  around  it  becomes  exceedingly  diffi- 
cult. Under  such  circumstances  one  cannot  be  surprised  that  even  distinguished 
anatomists  have  committed  mistakes.  Sir  Astley  Cooper  *  failed  in  one  instance. 
Uupuytren  perforated  the  artery  with  the  point  of  the  needle,  and  included  one  of 
the  nerves  in  the  ligature :  fatal  hemorrhage  was  the  result. t  We  were  present  at 
an  operation  in  which  the  large  nerve  (a  branch  of  the  brachial  plexus),  which 
runs  parallel  with  and  on  a  plane  anterior  to  the  artery,  was  mistaken  for  it  and 
tied,  the  surgeon  being  deceived  by  the  pulsation  communicated  to  the  nerve. 

The  description  of  the  means  whereby  the  collateral  circula- 
tion is  maintained  is  deferred  until  the  branches  of  the  subclavian 
have  been  made  out  and  described. 

Branches   of  the   Subclavian   Artery.  —  The  branches  of 
the  subclavian  extend  so  widely,  that  in  the  present  dissection 
we  can  trace  them  only  for  a  short 
distance.       They   are    four    in    num- 
ber :  — 

1.  The  vertebral. 

2.  The  thyroid  axis,  a  short,  thick 
trunk  which  gives  off  the  inferior 
thyroid,  supra-scapular,  and  posterior 
scapular. 

3.  The  internal  mammary. 

4.  The  superior  intercostal,  which 
gives  off  the  deep  cervical. 

As  a  rule,  the  vertebral,  the  thyroid 
axis,  and  the  internal  mammary  are 
given  off  from  the  subclavian  in  the 
first  part  of  its  course,  and  the  su- 
perior intercostal  in  the  second  part. 
The  most  frequent  deviation  is,  that 
the  posterior  scapular  (transversalis 
colli)  arises  from  the  subclavian  in  the 
third  part  of  its  course.  On  the  left 
side,  the  superior  intercostal  is  fre- 
quently given  off  in  the  first  part  of 
the  course  of  the  subclavian. 

Vertebral    Artery.  —  This,    the   first    and 


Fig.  49.  —  Branches  of  the  Subcla- 
vian Artery. 

I.  Innominate  artery.  2.  Common  ca- 
rotid artery.  3.  Subclavian  artery. 
4,  5.  Second  and  tliird  portions  of 
subclavian  artery  and  commencement 
of  axillary  artery.  6.  \'ertebral  ar- 
tery. 7.  Inferior  tbyroid  artery. 
8,  Ihyroid  axis.  9.  Ascending  cer- 
vical artery.  10.  Profunda  cervicis 
artery.  u.  Transversalis  colli  ar- 
tery. 12.  Supra-scapular  artery. 
13.  Internal  mammary  artery.  14. 
Superior  intercostal  artery. 


arises  from   the   upper  and    back   part  of  the 


largest    branch, 
subclavian.      It 


*  London  Medical  Review,  vol.  ii,  p.  300. 

\  Edinburgh  Med.  and  Surg.  Journal,  vol.  xvi,  1820. 


134  VERTEBRAL    ARTERY. 

ascends  in  the  neck,  and  for  a  short  distance  lies  in  the  interval 
between  the  scalenus  anticus  and  the  longus  colli.  Here  it 
enters  the  foramen  in  the  transverse  process  of  the  six  cervical 
vertebras,  and  ascends  through  the  foramina  in  the  transverse 
processes  of  the  succeeding  vertebrae.  In  the  interval  between 
the  axis  and  the  atlas,  the  artery  makes  a  sigmoid  curve,  that  it 
may  not  be  stretched  in  the  rotation  of  the  head.  Having  trav- 
ersed the  foramen  of  the  atlas,  the  artery  curves  backwards 
along  the  groove  in  its  arch,  perforates  the  posterior  occipito- 
atlantal  ligament  and  the  dura,  then  enters  the  skull  through 
the  foramen  magnum,  and  unites  with  its  fellow  near  the  lower 
border  of  the  pons  to  form  the  basilar  artery. 

Directly  after  the  artery  is  given  off  from  the  subclavian,  it 
lies  behind  the  internal  jugular  vein,  the  inferior  thyroid  artery, 
and  the  vertebral  vein,  and,  on  the  left  side,  behind  the  thoracic 
duct.  As  it  lies  upon  the  groove  on  the  neural  arch  of  the  atlas, 
it  is  separated  from  it  by  the  suboccipital  nerve,  and  is  situated 
within  the  suboccipital  triangle.  After  it  has  passed  through 
the  foramen  magnum,  the  artery  turns  round  the  medulla,  and 
is  placed  between  the  hypoglossal  nerve  and  the  anterior  root  of 
the  suboccipital  nerve. 

The  vertebral  artery  is  accompanied  by  slender  nerves  from 
the  inferior  cervical  ganglion  of  the  sympathetic.  These  nerves 
communicate  with  the  spinal  nerves  forming  the  brachial  plexus. 

Destined  for  the  brain,  the  vertebral  gives  off  no  branches  in 
the  neck,  except  a  few  small  muscular  ones  to  the  deeply  seated 
muscles,  and  which  anastomose  with  the  deep  cervical,  ascending 
cervical,  and  occipital  arteries;  it  furnishes,  however,  lateral 
spinal  branches  to  the  spinal  cord  and  its  membranes  which 
pass  through  the  intervertebral  foramina. 

Each  spinal  branch  divides  into  two  branches  ;  one,  passing 
along  the  root  of  the  spinal  nerve,  is  distributed  to  the  spinal 
cord  and  its  membranes  ;  the  other  ramifies  over  the  posterior 
surface  of  the  body  of  the  vertebra. 

The  cranial  branches  of  the  vertebral  artery  are  mentioned  at 
length  in  the  description  of  the  arteries  of  the  brain. 

The  vertebral  vein  is  formed  by  small  branches  from  the  mus- 
cles near  the  foramen  magnum.  It  descends  in  front  of  the 
artery  through  the  foramina  in  the  transverse  processes,  and, 
emerging  through  the  transverse  process  of  the  sixth,  crosses 
the  subclavian  artery  and  joins  the  brachio-cephalic  vein,  its  ori- 
fice  being  guardetl  by  a  single  or  a  double  valve.      It  receives 


THYROID    AXIS.  I  35 

the  veins  from  the  ncighborinii;  muscles — the  dorsi-spinal  veins, 
veins  from  the  spinal  canal,  the  deep  and  ascending  cervical,  and 
the  first  intercostal  veins.  In  some  subjects  it  communicates 
with  the  lateral  sinus  by  a  branch  through  the  posterior  condy- 
lar foramen. 

The  cervical  nerves  pass  through  the  intervertebral  foramina 
behind  the  vertebral  artery,  so  that  the  artery  runs  behind  its 
vein  and  m  front  of  the  nerves. 

Thyroid  Axis. — The  thyroid  axis  arises  from  the  subcla- 
vian near  the  inner  edge  of  the  scalenus  anticus,  and  after  a 
course  of  a  quarter  of  an  inch  (6.2  mm.)  divides  into  three 
branches,  which  take  different  directions  —  namely,  the  inferior 
thyroid,  the  supra-scapular,  and  the  posterior  scapular. 

1.  The  tit/crior  thyroid  artery  ascends  tortuously  behind  the  sheath  of  the 
common  carotid  and  the  sympathetic  nerve,  to  the  deep  surface  of  the  thyroid 
body,  in  which  it  communicates  freely  with  the  superior  thyroid  and  with  its  fel- 
low. Besides  small  branches  to  the  trachea,  the  oesophagus,  and  the  larynx,  it 
gives  off  — 

The  ascending  cervical  artery,  which  runs  up  close  to  the  spine,  between  the 
scalenus  anticus  and  the  rectus  capitis  anticus  major,  and  terminates  in  small 
branches,  some  of  which  supply  these  muscles ;  others  enter  the  intervertebral 
foramina,  and  supply  the  spinal  cord,  and  its  membranes.  It  anastomoses  with 
the  vertebral  and  ascending  pharyngeal  arteries. 

2.  The  supra-scapular  artery  (transversalis  humeri)  runs  outwards  over  the 
scalenus  anticus,  covered  by  the  sterno-mastoid  m.,  then  directly  bcncalh  and  par- 
allel with  the  clavicle:  crossing  over  the  third  part  of  the  subclavian  artery,  it 
passes  beneath  the  posterior  belly  of  the  omohyoid  to  the  superior  border  of  the 
scapula.  Here  it  is  covered  by  the  trapezius,  passes  abm'c  the  transverse  ligament 
which  bridges  over  the  notch ;  it  gives  off  some  branches  which  ramify  in  the 
supraspinous  fossa,  and  a  large  communicating  branch  which  passes  behind  the 
neck  of  the  scapula  to  reach  the  infra-spinous  fossa,  and  inosculates  freely  in  the 
infra  spinous  fossa  with  the  dorsalis  scapul.x,  a  branch  of  the  sub-scapular,  and 
with  the  posterior  scapular  artery.  Near  the  notch  it  is  joined  by  the  supra- 
scapular nerve,  which  runs  through  it.  The  branches  of  this  artery  are  numerous 
but  small,  and  are  as  follows :  the  inferior  stcrno-masloid  ^y>- ^l) 'i  the  supra-acro- 
mial,  which  anastomoses  with  the  acromio-thoracic  artery ;  articular  branches  to 
the  shoulder-joint;  the  tn/ra-spi>ious,  \\\\\c\v  ramifies  in  the  infra-spinous  fossa; 
and  the  sub-scapular,  which  ramifies  in  the  substance  of  the  sub-scapularis  muscle. 

3.  The  transversalis  colli  artery,  of  which  the  normal  origin  is  said  to  be  from 
the  thyroid  axis,  very  frequently  arises  from  the  subclavian  in  the  last  part  of  its 
course.  It  is  larger  than  the  preceding  artery,  and  runs  tortuously  across  the  side 
of  the  neck  (higher  than  the  supra-scapular),  over  the  scalene  muscles  and  the 
great  nerves  of  the  brachial  plexus  (sometimes  between  them),  and  cUvides  into 
two  branches,  the  superficial  cervical  and  the  posterior  scapular.  'YXxq  posterior 
scapular  disappears  beneath  the  trapezius  and  the  levator  anguli  scapulae  to  reach 
the  superior  angle  of  the  scapula.  It  then  runs  beneath  the  rhomboid  muscles, 
which  it  supplies,  down  to  the  inferior  angle  of  the  scapula,  anastomosing  freely 
with  the  terminations  of  the  supra-  and  sub-scapular  arteries,  and  with  the  poste- 
rior branches  of  some  of  the  intercostal  arteries.  The  superficial  cervical  is  given 
off  in  the  space  between  the  sterno-mastoid  and  trapezius.  This  vessel  proceeds 
tortuously  across  the  posterior  triangle  of  the  neck  to  the  under  surface  of  the 
trapezius,  to  which,  with  the  levator  anguli  scapulas,  it  is  principally  distributed. 

The  superficialis  colli  often  comes  direct  from  the  thyroid  axis. 


136  DEEP    CERVICAL    ARTERY. 

The  veins  corresponding  to  the  supra-scapular  and  posterior 
scapular  arteries  terminate  in  the  external  jugular,  sometimes  in 
the  subclavian.  The  middle  thyroid  vein  crosses  in  front  of  the 
common  carotid  artery,  and  joins  the  internal  jugular. 

Internal  Mammary. —  This  artery  arises  from  the  subcla- 
vian opposite  to  the  thyroid  axis.  It  descends  slightly  inwards 
behind  the  clavicle  and  the  subclavian  vein,  and  enters  the  chest 
between  the  cartilage  of  the  first  rib  and  the  pleura.  It  then 
passes  behind  the  costal  cartilages  about  half  an  inch  {12.^  mm.) 
from  the  border  of  the  sternum.  Its  further  course  will  be  ex- 
amined in  the  dissection  of  the  chest.  The  corresponding  vein, 
which  results  from  the  union  of  the  two  venae  comites,  most  fre- 
quently terminates  in  the  brachio-cephalic  vein. 

Superior  Intercostal.  — This  artery  is  given  off  by  the  sub- 
clavian behind  the  scalenus  anticus  on  the  right  side,  and  to  its 
inner  side  on  the  left,  so  that  you  must  divide  the  muscle  to  see 
it.  It  enters  the  chest  behind  the  pleura,  to  the  outer  side  of 
the  first  thoracic  ganglion  of  the  sympathetic.  It  runs  over  the 
necks  of  the  first  and  second  ribs,  and  furnishes  the  arteries  of 
the  two  upper  intercostal  spaces,  and  a  posterior  branch  which 
is  distributed  to  the  muscle  of  the  back  and  the  spinal  cord.  It 
usually  inosculates  with  the  first  intercostal  branch  of  the  aorta. 
The  corresponding  vein  terminates  on  the  right  side  in  the  vena 
azygos  major ;  on  the  left  in  the  brachio-cephalic. 

Deep  Cervical  Artery.  —  This  artery  arises  from  the  supe- 
rior intercostal,  seldom  direct  from  the  subclavian.  It  goes  to 
the  back  of  the  neck  between  the  first  rib  and  the  transverse 
process  of  the  seventh  cervical  vertebra,  and  ascends  between 
the  complexus  and  the  semi-spinalis  colli,  both  of  which  it  sup- 
plies. It  sometimes  inosculates  with  the  princeps  cervicis,  a 
branch  of  the  occipital  (p.  122). 

To  test  your  knowledge  of  the  branches  of  the  subclavian 
artery,  reflect  upon  the  answer  to  the  following  question  :  "  If 
the  artery  were  tied  in  the  first  part  of  its  course  before  it  gives 
off  any  branches,  how  would  the  arm  be  supi)lied  with  blood  }  " 
The  answer  is,  by  six  collateral  channels,  as  follow:  i.  By  the 
communications  between  the  superior  and  inferior  thyroid ; 
2.  Between  the  two  vertebral ;  3.  Between  the  internal  mam- 
mary and  the  intercostals  and  the  epigastric ;  4.  Between  the 
thoracic  branches  of  the  axillary  and  the  intercostal  branches  of 
the  aorta ;  5.  Between  the  superior  intercostal  and  the  aortic 
intercostals;    6.     Between  the  princeps  cervicis  and  the   deep 


BRACHIAL  PLEXUS  OF  NERVES. 


137 


cervical.     Most  of  these  inosculations  are  shown  in  the  diagram 
(Fig.  50). 

Again,  if  the  subclavian  were  tied  at  the  third  part  of  its 
course,  the  circulation  would  be  carried  on  by  the  communica- 
tions:  I.  Between  the  supra-scapular  and  the 
dorsalis  scapulae,  a  branch  of  the  subscapular ; 
2.  Between  the  supra-acromial  branch  of  the 
supra-scapular  and  the  acromio-thoracic ;  3. 
Between  the  posterior  scapular  and  the  sub- 
scapular and  dorsalis  scapulas ;  4.  Between 
the  internal  mammary,  the  aortic  intercostals 
and  superior  intercostal,  on  the  one  hand,  and 
the  long  and  short  thoracic  branches  of  the 
axillary,  on  the  other. 

Subclavian  Vein. — 
The  subclavian  vein  does 
not  form  an  arch  like  the 
artery,  but  proceeds  in  a 
nearly  straight  line  over 
the  first  rib  to  join  the 
internal  jugular.  It  ex- 
tends from  the  outer  mar- 
gin of  the  first  rib  to  mid- 
way between  the  inner 
border  of  the  scalenus  anti- 
cus  and  the  sterno-clavic- 
ular  articulation,  where  it 
joins  the  internal  jugular 
to  form  the  brachio-cephalic 
vein.  Throughout  its  whole 
course  the  vein  is  situated 
on  a  plane  anterior  to  and 
a  little  lower  than  the  ar- 
tery, from  which  it  is  sep- 
arated by  the  scalenus  anticus,  the  phrenic  and  pneumogastric 
nerves.  It  has  a  pair  of  valves  just  before  its  junction  with 
the  internal  jugular.  It  receives  the  anterior  jugular,  the  external 
jugular,  and  through  it  the  supra-scapular  and  posterior  scapular 
veins. 

Brachial  Plexus  of  Nerves.  —  The  large  nerves  forming 
the  plexus  which  supplies  the  upper  extremity  are  the  anterior 
divisions  of  the  four  lower  cervical  and  the  larger  portion  of  the 


Fig.  50. 


Diagram  to  show  the  Inosculations 
OP  THE  Subclavian  Aktery. 


138         BRANCHES  OF  THE  BRACHIAL  PLEXUS. 

first  thoracic,  with  a  small  fasciculus  derived  from  the  fourth  cer- 
vical nerve.  Emerging  from  the  intervertebral  foramina  the 
nerves  appear  between  the  anterior  and  middle  scalene  muscles, 
and  pass  with  the  subclavian  artery  into  the  axilla.  In  the  neck 
the  nerves  have  no  plexiform  arrangement,  and  it  is  only  in  the 
axilla  that  they  branch  and  communicate  largely  with  each  other, 
and  form  the  brachial  plexus  of  nerves.  The  nerves  in  the  neck 
are  wide  and  are  situated  higher  than  the  subclavian  artery,  and 
nearly  on  the  same  plane  ;  but  as  they  descend  beneath  the  clav- 
icle, they  converge  and  form  large  communications  with  each 
other,  thus  constituting  the  brachial  plexus  which  completely 
surrounds  the  artery  —  one  cord  lying  to  the  outer  side,  a  second 
lying  to  the  inner  side,  and  a  third  behind  the  vessel. 

The  plexus  is  crossed  superficially  by  the  omo-hyoid  muscle, 
and  by  the  supra-scapular  and  posterior  scapular  arteries,  and 
their  corresponding  veins. 

The  arrangement  of  the  nerves  in  the  formation  of  the  plexus 
is  very  variable,  and  often  not  alike  on  both  sides.  The  most 
usual  arrangement  is  that  at  the  outer  border  of  the  scalenus 
anticus  the  fifth  and  sixth  cervical  nerves  unite  to  form  an  upper 
trunk ;  the  eighth  and  the  first  thoracic  n.  form  a  lower  trunk  ; 
the  seventh  cervical  runs  for  some  distance  alone,  and  forms  a 
middle  trunk.  Now  each  of  these  four  upper  primary  nerves 
divides  into  an  anterior  and  a  posterior  branch  :  the  anterior 
branches  given  off  from  the  fifth,  sixth,  and  seventh  form  the 
outer  cord  of  the  plexus ;  the  anterior  branches  given  off  from 
the  eighth  cervical  and  first  thoracic  form  the  inner  cord ;  while 
the  posterior  branches  of  all  the  nerves  (namely,  the  fifth,  sixth, 
seventh,  and  eighth  cervical)  unite  to  form  \.hQ  posterior  cord  * 

The  branches  arising  from  the  plexus  are  best  arranged  into 
those  given  off  above  the  clavicle,  and  those  given  off  below  it. 
The  following  are  those  given  off  above  the  clavicle. 

a.  The  branch  forming  one  of  the  roots  of  the  phrenic  arises 
from  the  fifth  cervical.      {Not  in  diagram  51  p.  139.) 

b.  Nerve  to  the  snbclavijis  m.  —  This  proceeds  from  the  fifth 
and  sixth  cervical,  and  crosses  the  subclavian  artery  in  the  third 
part  of  its  course.  It  frequently  sends  a  filament,  which  passes 
in  front  of  the  subclavian  vein  to  join  the  phrenic  nerve. 

*  Very  frecjuently  the  posterior  l)ianch  of  the  eighth  cervical  nerve  does  not, 
strictly  speaking,  form  part  of  flie  posterior  cord,  but  is  continued  on  as  a  separate 
fasciculus  10  form  part  of  the  musculo-spiral  nerve.  For  a  description  of  the 
arrangement  of  the  nerves  constituting  the  plexus,  see  a  paper,  by  Lucas,  Guy's 
l/ospiliil  Rcf'orls    1S75;  also  Turner,  in  the yw//-;/;// <y  Anatomy,  1872. 


BRANCHES  OF  THE  BRACHIAL  PLEXUS.  1 39 

c.  Nerves  to  the  scaleni  and  the  longus  colli  muscles  are  given 
off  from  the  lower  cervical  nerves  as  they  leave  the  interverte- 
bral foramina. 

d.  Ncn'e  to  the  rhomboid  muscles.  —  This  arises  from  the 
fifth  cervical  nerve,  passes  through  the  scalenus  medius,  and 
accompanies  the  posterior  scapular  artery,  beneath  the  levator 
anguli  scapulae,  which,  as  well  as  the  rhomboid  muscles,  it 
supplies. 

e.  T\\Q  supra-scapular  wQwc  ^in^c's,  from  the  cord  formed  by 
the  fifth  and  sixth  cervical  n.,  runs  to  the  upper  border  of  the 


Fig.  51.  —  Diagram  of  the  Formation  of  the  Brachial  Plexus  and  its  Branches. 
c  4-8.  Anterior  trunks  of  the  cervical  nerves.  D  i.  Anterior  trunk  of  the  first  thoracic  n.  q.  N.  to 
the  rhomboid  m.  10.  Supra-scapular.  11.  N.  to  subclavius  m.  12-13.  Anterior  thoracic. 
14,15,16.  Subscapular  n.  17.  Lesser  int.  cutaneous.  18  Musculo-cutaneous.  19.  Circum- 
flex. 20.  Median.  21.  Musculo-spiral.  22.  Ulnar.  23.  Int.  cutaneous.  24.  Ext.  respira- 
tory of  Bell 

scapula,  where  it  meets  with  the  corresponding  artery,  and  then 
passes  through  the  notch  in  the  scapula.  In  the  supra-spinous 
fossa  it  gives  off  two  branches  to  the  supra-spinatus  m.,  and  an 
upper  articular  branch  to  the  shoulder ;  it  then  descends  behind 
the  acromion  process  to  the  infra-spinous  fossa,  distributing  a 
branch  to  the  infra-spinatus  muscle,  and  a  lower  articular  fila- 
ment to  the  shoulder  joint. 

f.    The  posterior  thoracic  nerve  (called  external  respiratory  by 
Sir  C.  Bell)  to  the  serratus  magnus  arises  from  the  fifth  and 


140  TEMPORAL    AND    PTERYGO-M AXILLARY    REGIONS. 

sixth  cervical  (sometimes  also  from  the  seventh)  in  the  substance 
of  the  scalenus  medius.  It  passes  through  this  muscle  and  sub- 
sequently emerges  below  the  rhomboid  nerve ;  it  then  descends 
behind  the  brachial  plexus  and  the  subclavian  vessels  to  the 
outer  surface  of  the  serratus  magnus,  to  the  several  digitations 
of  which  it  is  exclusively  distributed. 

o-.  An  articular  brancJi  is  distributed  to  the  shoulder  joint, 
besides  some  filaments  to  the  constituent  bones. 

It  only  remains  to  be  observed  that  the  upper  cord  of  the 
brachial  plexus  receives  a  branch  from  the  lower  cord  of  the 
cervical,  and  that  each  of  its  component  nerves  communicates  by 
slender  filaments  with  the  sympathetic. 

Beloiv  the  clavicle  the  plexus  gives  off  branches  for  the  supply- 
of  the  arm  ;  namely,  from  the  oiiter  cord,  the  external  anterior 
thoracic  (to  the  pect oralis  major),  the  musculo-cutaneous,  and 
the  outer  head  of  the  median  ;  from  the  inner  cord,  the  internal 
anterior  thoracic  n.  (to  the  pectoralis  minor),  the  inner  head  of 
the  median,  the  ulnar,  the  internal  cutaneous,  and  the  lesser  in- 
ternal cutaneous  (ncjve  of  Wrisberg)  nerves;  from  the  posterior 
cord,  the  three  subscapular  (to  the  subscapularis,  the  latissimus 
dorsi,  and  teres  major),  the  circumflex  (to  the  deltoid  and  teres 
minor),  and  the  musculo-spiral  nerves :  all  of  which  will  be  de- 
scribed more  fully  in  the  dissection  of  the  upper  extremity. 


TEMPORAL    AND    PTERYGO-MAXILLARY 
REGIONS. 

In  this  dissection  the  parts  should  be  examined  in  the  follow- 
ing order  :  — 

1.  Superficial  and  deep  fasciae.  5.    Temporal  muscle. 

2.  Superficial  arteries  and  nerves  of       6.    Pterygoid  muscles. 

the  temple.  7.    Internal      maxillary    artery      and 

3.  Masseter  muscle.  branches. 

4.  Temporal  aponeurosis.  8.    Mandibular  nerves  and  branches. 

To  expose  the  temporal  region,  the  skin  of  the  temple  should 
be  reflected  from  below  upwards.  Beneath  the  skin  you  come 
upon  a  layer  of  tough  connective  tissue,  continuous,  above,  with 
the  aponeurosis  of  the  scalp  ;  below,  with  the  fascia  covering  the 
masseter  and  the  parotid  gland.  In  this  tissue  are  contained  the 
superficial  temporal  vessels  and  nerves. 


TEMPORAL    AKTP:KY. 


141 


Temporal  Artery.  — This  is  the  smaller  of  the  two  terminal 
branches  of  the  external  carotid.  Arising  in  the  substance  of  the 
parotid  gland  near  the  neck  of  the  mandible,  it  passes  over  the 
root  of  the  zygoma,  close  to  the  meatus  auditorius  externus,  as- 
cends for  about  i^  inches  {J. 8  cm.)  on  the  temporal  fascia,  and 
there  divides  into  an  anterior  and  a  posterior  branch.  Above  the 
zygoma  it  is  superficial,  being  covered  only  by  the  attrahens  aurem 


Fig.  52. 

and  a  strong  layer  of  fascia ;  here  it  is  accompanied  by  branches 
of  the  facial  nerve,  and  by  the  auriculo-temporal  branch  of  the 
inferior  division  of  the  fifth  nerve.  It  gives  off  the  following 
branches  :  — 

a.  Several  small  branches  to  ihe parotid gla?td,  the  temporomandibular  articu- 
lation, and  the  massctcr. 

b.  The  transversalis  faciei  (p.  57). 

c.  The  anterior  auricular  branches,  two  in  number,  superior  and  inferior, 
ramify  on  the  front  of  the  pinna  of  the  ear,  inosculating  with  branches  of  the 
posterior  auricular. 


142  AURICULO-TEMPORAL    NERVE. 

d.  The  middle  temporal,  a  small  vessel  given  off  while  the  artery  is  still  in  the 
parotid  gland,  pierces  the  temporal  fascia  above  the  zygoma,  and  running  in  the 
substance  of  the  temporal  muscle  anastomoses  with  the  temporal  branches  of 
the  internal  maxillary. 

Of  the  two  branches  into  which  the  temporal  divides,  the  anterior  runs  tortu- 
ously towards  the  external  angle  of  the  frontal  bone,  distant  from  it  about  an  inch. 
Its  ramifications  extend  over  the  forehead,  supplying  the  orbicularis  and  occipito- 
frontalis  m.,  and  inosculate  with  the  supra-orbital  and  frontal  arteries.  The  pos- 
terior runs  towards  the  back  of  the  head,  and  inosculates  freely  with  the  occipital 
and  posterior  auricular.  The  anterior  branch,  although  the  smaller,  is  usually 
selected  for  arteriotomy,  the  posterior  being  covered  by  a  strong  and  unyielding 
fascia. 

The  temporal  vein  is  formed  by  the  junction  of  the  veins  ac- 
companying the  terminal  branches  of  the  temporal  artery,  which 
are  situated  superficial  to  the  arteries  ;  just  above  the  zygoma  it 
is  joined  by  the  middle  temporal  vein  which  takes  its  origin  from 
a  plexus  in  the  temporal  fossa.  The  common  temporal  vein, 
formed  by  the  union  of  these  three  veins,  passes  over  the  zygoma, 
enters  the  parotid  gland,  and  joins  the  internal  maxillary  vein  to 
form  the  temporo-maxillary  vein, 

Auriculo-temporal  Nerve.  —  This  nerve  supplies  the  tem- 
ple and  side  of  the  head  with  common  sensation.  It  arises,  close 
to  the  foramen  ovale,  from  the  third  division  of  the  fifth  pair  by 
two  roots  (between  which  the  middle  meningeal  or  mididural 
artery  runs).  From  its  origin  it  proceeds  outwards  beneath  the 
external  pterygoid,  between  the  neck  of  the  mandible  and  the 
internal  lateral  ligament.  It  then  ascends  beneath  the  parotid, 
over  the  root  of  the  zygoma,  where  it  accompanies  the  temporal 
artery,  and  divides,  like  it,  into  an  anterior  and  a.  posterior  branch 
(Fig.  33,  p.  83). 

The  posterior  branch  is  the  smaller  of  the  two  ;  the  anterior 
forms  communications  with  the  temporal  branches  of  the  facial, 
and  the  orbital  branch  of  the  maxillary.  The  ramifications  of 
the  nerve  correspond  with  those  of  the  artery. 

Near  their  origin  the  roots  of  the  nerve  are  connected  by  fine 
filaments  with  the  otic  ganglion,  and  close  to  the  condyle  of  the 
mandible  the  nerve  sends  round  the  external  carotid  artery  two 
coimminicating  branches  to  the  temporo-facial  branch  of  the  facial 
nerve.  It  here  distributes  parotid  branches  to  the  gland  ;  artic- 
nlar  branches  to  the  temporo-mandibular  articulation,  to  the 
meatus  auditorius  and  the  membrana  tympani.  Above  the  zy- 
goma it  gives  off  tivo  auricular  filaments  ;  the  upper  ramifies  in 
the  skin  of  the  outer  aspect  of  the  ear,  mainly  on  the  tragus  and 
upper  half  of  the  auricle  ;  the  /^zi/^r  supplies  the  lobule  and  lower 
part  of  the  pinna. 


MASSETER    MUSCLE.  I43 

Lastly,  in  the  subcutaneous  tissue  of  the  temple,  we  find  the 
temporal  branches  of  the  facial  nerve,  which  supply  the  frontalis, 
the  attrahens  aurem,  the  orbicularis  palpebrarum,  tensor  tarsi, 
and  corrugator  supercilii. 

Masseter  Muscle.  —  This  muscle  arises  from  the  lower  edge 
of  the  zygoma,  and  is  inserted  into  the  outer  side  of  the  ramus 
and  coronoid  process  of  the  mandible.  The  masseter  is  com- 
posed of  superficial  and  deep  fibres  which  cross  like  the  letter  X, 
The  siipei-ficial  fibres,  constituting  the  principal  part  of  the  mus- 
cle, arise  from  the  anterior  two-thirds  of  the  zygoma  by  tendi- 
nous fibres  which  occupy  the  front  border  of  the  muscle,  and  send 
aponeurotic  partitions  into  its  substance.  These  fibres  pass 
downwards  and  backwards,  this  direction  giving  them  greater 
advantage,  and  are  inserted  into  the  angle  and  part  of  the  ramus 
of  the  mandible.  The  deep  fibres,  mainly  muscular  (which  are 
concealed  by  the  parotid  gland),  arise  from  the  posterior  third 
of  the  zygoma,  incline  forwards,  and  are  inserted  into  the  upper 
half  of  the  ramus  and  the  coronoid  process.  Besides  these,  a 
few  fibres,  arising  from  the  inner  surface  of  the  zygoma,  are 
inserted  into  the  coronoid  process  and  the  tendon  of  the  tem- 
poral muscle.  Its  action  is  to  raise  the  mandible  and  help  to 
masticate  the  food.     Its  nerve  comes  from  the  mandibular. 

The  following  objects  lie  superficial  to  the  masseter :  i.  Zy- 
gomatici  major  and  minor ;  2.  Orbicularis  palpebrarum  ;  3. 
Glandula  socia  parotidis  and  parotid  duct ;  4.  Transversalis 
faciei  artery;  5.  Facial  artery  and  vein;  6.  Branches  of  the 
facial  nerve. 

Temporal  Fascia.  —  This  strong,  shining  aponeurotic  mem- 
brane covers  the  temporal  muscle,  its  chief  use  being  to  give  ad- 
ditional origin  to  its  fibres.  It  is  attached  above  to  the  temporal 
ridge,  and,  increasing  in  thickness  as  it  descends,  divides  near 
the  zygoma  into  two  layers,  which  are  attached  to  the  outer  and 
inner  borders  of  the  zygomatic  arch.  These  layers  are  sepa- 
rated by  fat,  in  which  is  found  a  filament  from  the  orbital  branch 
of  the  maxillary  nerve,  and  the  orbital  branch  of  the  temporal 
artery.  The  density  of  this  aponeurosis  explains  why  abscesses 
in  the  temporal  fossa  rarely  point  outwards  ;  the  pus  generally 
makes  its  way,  beneath  the  zygoma,  into  the  mouth. 

Reflect  the  aponeurosis,  and  notice  that  it  is  separated  from 
the  temporal  muscle,  near  the  zygoma,  by  fat.  The  absorption 
of  this  fat,  and  the  wasting  of  the  muscle,  occasion  the  sinking 
of  the  temple  in  emaciation  and  old  age. 


144 


TEMPORAL    MUSCLES. 


Dissection.  —  Divide  the  zygomatic  arch  on  each  side  of  the 
masseter,  and  turn  it  downwards,  taking  care  of  the  masseteric 
nerve  and  artery  which  enter  its  under  aspect.  Observe  the 
direction  of  the  superficial  and  deep  fibres,  and  the  tendinous 
partitions  which  augment  the  power  of  the  muscle  by  increasing 
its  extent  of  origin.  The  masseteric  nerve  and  artery  enter  the 
under  surface  of  the  muscle  near  to  its  posterior  border,  through 
the  sigmoid  notch  of  the  mandible  ;  the  artery  comes  from  the 
internal  maxillary,  the  nerve  from  the  motor  division  of  the  man- 
dibular, 


Fig.  S3. 

Temporal  Muscle.  — This  broad,  fan-shaped  muscle  aj^ises 
from  the  whole  of  the  temporal  fossa  (except  the  malar  surface) 
and  the  deep  surface  of  the  temporal  fascia.  Its  fibres  converge 
to  a  strong  tendon,  which  is  inserted  into  the  inner  surface,  the 
apex,  and  anterior  border  of  the  coronoid  process,  as  far  for- 
wards as  the  last  molar  tooth. 

The  fibres  of  the  muscle,  converging  from  their  wide  origm, 
pass  under  the  zygomatic  arch,  and  terminate  upon  their  ten- 
don, the  outer  surface  of  which  is  partially  concealed  by  the  in- 
sertion of  those  fibres  which  come  from  the  temporal  aponeurosis  : 


EXTERNAL    PTERYGOID.  1 45 

remove  them,  and  see  how  this  tendon  radiates  into  the  muscle 
like  the  ribs  of  a  fan.  Its  nerves  (two  deep  temporal)  are 
branches  of  the  mandibular  (p.  146). 

Between  the  posterior  border  of  this  muscle  and  the  neck  of 
the  mandible,  the  masseteric  nerve  and  artery  pass  to  their  des- 
tination ;  in  front  of  the  muscle  the  buccal  branch  of  the  man- 
dibular nerve  descends  to  the  buccinator  with  its  companion 
artery. 

The  temporal  muscle  is  in  relation  on  its  deeper  surface  with 
the  external  pterygoid  and  buccinator  muscles,  the  internal 
maxillary  artery  and  vein,  and  the  deep  temporal  arteries  and 
nerves. 

Pterygo-maxillary  Region.  —  The  zygomatic  arch  having 
been  already  divided,  the  structures  should  be  cleaned  so  as  to 
expose  the  coronoid  process  of  the  mandible,  the  insertion  of 
the  temporal  muscle,  and  the  loose  fat  which  surrounds  it. 
Next,  saw  through  the  coronoid  process  in  a  direction  down- 
wards and  forwards,  so  as  to  include  the  insertion  of  the  mus- 
cle, and  reflect  it  upwards  without  injuring  the  subjacent 
vessels  and  nerves. 

Dissection.  —  To  gain  a  good  view  of  the  muscles,  nerves, 
and  vessels  of  the  pterygo-maxillary  region,  a  portion  of  the  as- 
cending ramus  of  the  mandible  must  be  removed  with  a  Hey's 
saw,  as  shown  in  Fig.  54,  p.  146. 

In  this  region  we  have  to  examine  the  two  pterygoid  muscles, 
the  trunk  and  branches  of  the  internal  maxillary  artery,  the 
mandibular  nerve,  and  the  internal  lateral  ligament  of  the  man- 
dible. All  these  structures  are  imbedded  in  loose  soft  fat,  which 
must  be  cautiously  removed  without  injuring  them. 

External  Pterygoid.  —  This  muscle  arises  by  two  heads,  one, 
the  upper,  from  the  great  wing  of  the  sphenoid  and  from  the 
ridge  pterygoid  ;  the  lower,  from  the  outer  surface  of  the  external 
pterygoid  plate,  a  few  fibres  taking  origin  from  the  outer  side 
of  the  tuberosities  of  the  palate  and  maxillary  bones.  The 
muscle  passes  horizontally  backwards  and  is  inserted  into  the 
neck  of  the  mandible,  and  slightly  into  the  border  of  the  inter- 
articular  fibro-cartilage  of  the  temporo-mandibular  articulation. 
It  is  supplied  by  a  muscular  branch  from  the  mandibular  n. 

The  advantage  of  the  insertion  of  some  of  its  fibres  into  the 
inter-articular  cartilage  is,  that  the  cartilage  follows  the  condyle 
in  all  its  movements.  When  the  mandible  is  dislocated,  it  is 
chiefly  by  the  action  of  this  muscle,  which  draws  the  condyle 


146 


PTERYGOID    MUSCLES, 


forwards  into  the  zygomatic  fossa,  the  inter-articular  cartilage 
being  dislocated  with  the  condyle. 

Relations  of  External  Pterygoid. — By  its  deep  surface 
the  muscle  is  in  relation  with  the  internal  pterygoid  m.,  the 
internal  lateral  ligament,  the  anteria  meningea  media  or  midi- 
dumlis,  the  auriculo-temporal,  the  gustatory,  the  inferior  dental, 
and  chorda  tympani  nerves,  and  occasionally  with  the  internal 
maxillary  artery.  Between  its  two  heads  of  origin  the  buccal 
and  anterior  deep  temporal  nerves  emerge. 


Anterior  deep  temporal  n.  and  a 


External  pterygoid  m. 

Posterior  deep  temporal  n.  and  a. 
I  Masseteric  n.  and  a. 


Infra- 
orbital a. 
Spheno- 
maxillary 
fossa. 
Superior 
dental  a. 

Buccal  a. 


Parotid        '^ 
duct. 

Buccal  n. 

Pterygo- 
mandib- 
ular lig- 
ament. 


Inter- 
articular 
fibro-car- 
tilage. 

Temporal 
artery  and 
auriculo- 
temporal 
nerve. 

Middle 
meningeal 


Inferior  dental  a. 
Inferior  dental  n. 
Gustatory  n. 
—  Mylo-liyoid  n. 

Internal  ptery- 
goid m. 


Fig.  54. —  Pterygoid  Muscles  and  Internal  Maxillary  Artery. 


Internal  Pterygoid. — This  muscle  arises  by  musculo-ten- 
dinous  fibres  from  the  inner  surface  of  the  external  pterygoid 
plate  of  the  sphenoid  bone  and  from  that  portion  of  the  tuber- 
osity of  the  palate  bone  which  forms  the  lower  part  of  the  ptery- 
goid fossa,  also  by  a  smaller  slip  in  front  of  the  external  pterygoid 
from  the  external  surface  of  the  tuberosities  of  the  palate  and 
maxillary  bones.  It  is  ijiscrtcd  into  the  rough  surface  on  the 
inner  side  of  the  angle  of  the  mandible,  as  high  as  the  dental 
foramen.  It  is  supplied  by  a  muscular  branch  from  the  mandib- 
ular n. 


INTERNAL    MAXILLARY    ARTKRY.  I47 

Relations  of  the  Internal  Pterygoid. — The  internal 
pterygoid  is  in  relation  superficially  with  the  external  pterygoid, 
the  internal  lateral  ligament,  the  internal  maxillary  artery  and 
vein,  the  mandibular  vessels  and  nerve,  the  mylo-hyoid  artery 
and  nerve,  the  chorda  tympani,  and  the  buccal  nerves  ;  by  its 
deep  surface,  with  the  tensor  palati  and  superior  constrictor 
muscles. 

Notice  particularly  the  direction  of  the  fibres  of  the  ptery- 
goid muscles.  The  fibres  of  the  external  run  horizontally  out- 
wards and  backwards  from  their  origin  ;  the  fibres  of  the  in- 
ternal run  downwards,  backwards,  and  outwards  from  their  origin. 
The  internal  pterygoid  has  tendinous  septa  like  the  masseter. 

Action  of  Pterygoid  Muscles. — The  internal  pterygoid 
raises  the  mandible,  acting  in  concert  with  the  temporal  and 
masseter  muscles ;  it  moreover  assists  the  external  pterygoid 
and  anterior  part  of  the  masseter  to  draw  the  mandible  forwards. 
The  external  pterygoid  draws  the  mandible  forwards  and  some- 
what to  the  opposite  side,  and  also  in  conjunction  with  the  inter- 
nal pterygoid  produces  the  lateral  movements  of  the  mandible 
essential  to  the  mastication  of  the  food.  Consequently  they  are 
enormously  developed  in  all  ruminants  and  comparatively  feebly 
in  carnivorous  animals.  The  antagonistic  muscles  of  the  forward 
action  of  the  two  pterygoids  are  the  temporal  m.  and  the  deep 
fibres  of  the  masseter. 

Dissection.  —  Saw  through  the  neck  of  the  mandible,  disar- 
ticulate the  condyle  with  its  fibro-cartilage  from  the  glenoid  cav- 
ity, and  turn  it  forwards  with  the  external  pterygoid,  so  that  the 
condyle  can  be  replaced  if  desirable.  A  little  dissection  will 
bring  into  view  the  internal  lateral  ligament,  the  internal  max- 
illary artery  and  vein,  the  mandibular  nerve  and  its  branches, 
and  the  chorda  tympani  nerve. 

Internal  Maxillary  Artery.  — This  is  the  larger  of  the  two 
terminal  branches  into  which  the  external  carotid  divides,  oppo- 
site the  neck  of  the  mandible  in  the  parotid  gland.  It  passes 
horizontally  forwards  between  the  neck  of  the  mandible  and  the 
internal  lateral  ligament,  then  runs  tortuously,  in  some  cases 
above,  in  others  beneath,  the  external  pterygoid,  enters  the 
spheno-maxillary  fossa  between  the  two  heads  of  the  external 
pterygoid,  where  it  terminates  by  dividing  into  numerous 
branches. 

The  course  of  this  artery  is  divided  into  three  stages.  In 
\hQ  first,  the  artery   lies  between  the  neck  of  the  mandible  and 


148 


INTERNAL    MAXILLARY. 


the  internal  lateral  ligament  ;  in  the  second,  it  lies  either  over  or 
under  the  external  pterygoid  ;  in  the  third,  it  lies  in  the  spheno- 
maxillary fossa. 


INCISWS 


Fig.  55.  —  Internal  Maxillary  Artery. 


BRANCHES    OF  THE    INTERNAL    MAXILLARY    ARTERY  IN  THE 
THREE  STAGES  OF  ITS  COURSE. 


Branches  in  the  First 
Stage. 

a.  Tympanic. 

b.  Meningea  (magna) 

media,  or  viidi- 
dicralis. 

c.  Meningea  parva,  or 

parviduralis. 

d.  Mandibular. 


Brafiches  in  the  Second 
Stage. 
Six  to  the  fii%'e  muscles  of 
mastication,  namely  : 

e.  Masseteric. 

f.  Anterior  and  posterior 

deep  tempo  al. 

g.  E.xternal    and    internal 

pteiygoid. 
h.    Buccal. 


Brafiches  in  the  Third 

Stage. 
i.    Superior  dental. 
j.    Infra-orbital. 
k.    Descending  palatine. 
/.    Vidian. 
rn.    Ptery go-palatine. 
71.   Nasal  or  spheno-pal- 
atine. 


Branches  in  the  First  Part.  —  a.  The  tympanic  ascends  behind  the  articu- 
lation of  the  mandible,  and  passes  through  the  Gasserian  fissure  to  the  tympanum. 
It  supplies  that  cavity  and  the  membrana  tympani,  and  anastomoses  with  the 
stylomastoid  and  Vidian  arteries.  It  occasionally  gives  off  a  deep  auricular 
branch  which  pierces  the  anterior  wall  of  the  external  auditory  meatus,  supplying 
the  skin  of  this  canal.  This  artery  is  not  infrequently  given  off  from  a  branch  of 
the  internal  maxillary  artery. 


BRANCHES  OF  THE  INTERNAL  MAXILLARY  ARTERY. 


149 


o.  The  middle  {large)  vicningcal  ox  mididural  artery  ascends  between  the  two 
roots  of  the  auriculo-teniporal  nerve,  behind  the  external  pterygoid,  and  enters 
through  the  foramen  spinosum  into  the  cranium,  where  it  ramities  between  the  dura 
and  the  bones.  In  the  skull  it  gives  off  small  branches  to  the  Gasserian  ganglion  , 
2l petrosal  branch  passing  through  the  hiatus  Fallopii ;  d^r^/A// branches  entering  the 
orbit  through  the  sphenoidal  fissure ;  and  temporal  branches  which  pierce  the 
great  wing  of  the  sphenoid  to  enter  the  temporal  fossa.  Its  further  course  is 
described  at  p.  t,},. 

c.  The  meniitgea  parva  {small)  or  parvidural  ascends  through  the  foramen  ovale 
into  the  skull,  and  supplies  chiefly  the  ganglion  of  the  fifth  cranial  nerve.  It  often 
comes  from  the  meningea  media. 

d.  The  mandibular  or  inferior  dental  artery  descends  behind  the  neck  of  the 
mandible  to  the  dental  foramen,  which  it  enters  with  the  dental  or  mandibular 
nerve.  It  then  proceeds  through  a  canal  in  the  diploe  to  the  symphysis,  where 
it  minutely  inosculates  with  its  fellow.  In  this  canal,  which  runs  beneath  the 
roots  of  all  the  teeth,  the  artery  gives  branches  which  ascend  through  the  little 


Third  part.  Second  Part.  First  Part. 

Fig,  56.    Plan  of  Internal  Maxillary  Artery. 


foramina  in  the  fangs,  and  supply  the  pulp  in  their  interior.  Opposite  the  fora- 
men mentale  arises  the  mental  branch  already  described  (p.  6).  Before  entering 
the  dental  foramen  the  artery  furnishes  a  small  branch  —  mylo-hyoid  —  which  ac- 
companies the  nerve  proceeding  to  the  mylohyoid  muscle. 

Branches  in  the  Second  Part. — e.  The  ?nasseteric  branch  passes  through 
the  sigmoid  notch  of  the  mandible  behind  the  temporal  muscle  to  the  under  sur- 
face of  the  masseter,  with  the  masseteric  nerve,  and  inosculates  with  the  facial 
and  transverse  facial  arteries. 

f.  The  anterior  and  posterior  deep  temporal  arteries  ascend  to  supply  the  tem- 
poral muscle,  ramifying  between  the  muscle  and  the  bone,  one  near  the  front,  the 
other  near  the  posterior  border  of  the  muscle.  They  communicate  with  the 
superficial  and  middle  temporal  arteries,  with  the  terminal  branches  of  the  lachry- 
mal a.,  and  with  the  temporal  branches  of  the  arteria  mididuralis. 

g.  The  pterygoid  branches  supply  the  internal  and  external  pterygoid  muscles. 
h.   The  buccal  branch  runs  forward  with  the  buccal  nerve  to  the  buccinator, 

where  it  anastomoses  with  the  facial  artery. 


150   BRANCHES  OF  THE  INTERNAL  MAXILLARY  ARTERY. 

Branches  in  the  Third  Part.  —  /.  The  maxillary  or  sztpcrior  dental  branch 
runs  along  the  tuberosity  of  the  maxillary  bone,  and  sends  small  arteries  through 
the  foramina  in  the  bone  to  the  pulps  of  the  molar  and  bicuspid  teeth.  It  also 
supplies  the  gums  and  the  mucous  membrane  of  the  antrum. 

j.  The  infra  orbital  branch  ascends  through  the  sphenomaxillary  fissure,  then 
runs  forward  along  the  infra-orbital  canal  with  the  maxillary  neive,  and  emerges 
upon  the  face  at  the  infra-orbital  foramen,  beneath  the  levator  labii  superioris. 
In  the  infra-orbital  canal  the  artery  sends  branches,  anterior  dental,  downwaids 
through  little  canals  in  the  bone  to  the  incisor  and  canine  teeth,  and  upwards  into 
the  orbit  to  the  lachrymal  gland,  the  inferior  oblique,  and  inferior  rectus.  After 
issuing  from  the  foramen  it  sends  upwards  branches  to  the  lachrymal  sac,  and  de- 
scending branches  to  the  upper  lip.  The  former  anastomose  with  the  nasal 
branches  of  the  ophthalmic  and  facial  arteries ;  the  latter  with  the  superior  coro- 
nary, transverse  facial,  and  buccal  arteries. 

k.  Th.e  posterior  descending  palatine,  a  branch  of  considerable  size,  runs  down 
the  posterior  palatine  canal  with  the  palatine  nerve  (a  branch  from  Meckel's 
ganglion),  and  then  along  the  roof  of  the  hard  palate,  towards  the  anterior  pala- 
tme  canal,  in  which,  much  diminished  in  size,  it  inosculates  on  the  septum  nasi 
with  a  branch  of  the  spheno-palatine  artery.  It  supplies  the  gums,  the  glands,  and 
mucous  membrane  of  this  part,  and  furnishes  branches  to  the  soft  palate. 

/.  The  Vidian,  an  insignilicant  branch,  runs  backwards  through  the  Vidian 
canal  with  the  Vidian  nerve,  and  is  distributed  to  the  Eustachian  tube,  the  phar- 
ynx, and  the  tympanum. 

m.  T\\Q  pterygopalatine  is  a  small  but  constant  branch  which  runs  backwards 
through  the  ptengo-palaline  canal  with  the  pharyngeal  nerve  from  Meckel's  gan- 
glion, and  ramifies  upon  the  upper  part  of  the  pharynx  and  the  Eustachian  tube. 

;/.  The  nasal  or  spheno-palatine  branch  enters  the  nose  through  the  spheno- 
palatine foramen  in  company  with  the  nasal  nerve  from  Meckel's  (spheno-palatine) 
ganglion,  and  ramifies  upon  the  spongy  bones,  the  ethmoidal  cells,  and  the  an- 
trum. One  large  branch,  the  artery  of  the  septum,  runs  along  the  septum  nasi 
towards  the  anterior  palatine  canal,  where  it  joins  the  descending  palatine  artery. 

Observe  that  all  the  branches  of  the  internal  maxillary  artery 
in  the  first  and  third  parts  of  its  course  traverse  bony  canals, 
while  the  branches  in  the  second  part  go  directly  to  muscles. 

Pterygoid  Plexus  of  Veins.  — The  ijitcrnal  tnaxillaiy  vein 
is  formed  by  the  veins  corresponding  to  the  branches  of  the 
artery.  As  the  vein  lies  between  the  temporal  and  external 
pterygoid  muscles  it  forms  a  plexus — pterygoid plcxits  —  which 
communicates,  above,  with  the  cavernous  sinus  by  branches 
which  come  through  the  foramina  at*  the  base  of  the  skull  ;  in 
front  it  communicates  with  the  facial  vein.  It  joins  the  tempo- 
ral in  the  substance  of  the  parotid  gland,  and  thus  communicates 
with  the  external  jugular  vein. 

Mandibular  or  Third  Division  of  Fifth  N.  and  Branches. 
—  This  great  nerve  is  the  largest  of  the  three  divisions  of  the 
fifth  cerebral  nerve.  It  differs  from  the  other  two  divisions,  i.e., 
the  ophthalmic  and  the  maxillary,  in  that  it  contains  motor  as 
well  as  sensory  filaments,  the  motor  being  furnished  by  the  small 
non-ganglionic  root  of  the  fifth  nerve.  It  is  necessary  to  remem- 
ber this  point  of  its  physiology  in  order  to  understand  its  cxten- 


MANDIBULAR    DIVISION    OF    TUK    FIFTH    NERVE.  I5I 

sive  distribution;  for  the  sensory  portion  supplies  the  parts  to 
which  it  is  distributed  with  common  sensation  tnly,  whilst  the 
motor  portion  supplies  all  the  muscles  concerned  in  mastication. 
The  nerve,  composed  of  sensory  and  motor  filaments,  emerges 
from  the  skull  through  the  foramen  ovale,  into  the  zygomatic 
fossa,  as  a  thick  trunk,  under  the  name  of  the  mandibular.  It 
lies  directly  external  to  the  Eustachian  tube,  and  is  covered  by 
the  external  pterygoid  muscle,  which  must  be  turned  on  one 
side  to  expose  it.  Immediately  after  its  exit  from  the  skull,  the 
nerve  divides  into  two  parts,  an  anterior,  or  motor  division,  and 
a  posterior,  or  sensory  division.  From  the  anterior  portion 
(chiefly  motor)  are  derived  branches  distributed  to  the  muscles 
of  mastication  and  the  buccal  nerve.  From  the. posterior  (mainly 
sensory)  come  the  following  branches  :  the  auriculo-temporal, 
gustatory,  and  inferior  dental ;  there  are  also  motor  branches  to 
the  mylo-hyoid  and  anterior  belly  of  the  digastric.  This  appar- 
ent anomaly  will  be  presently  explained. 

BRANCHES    OF   THE   MANDIBULAR    DIVISION    OF    THE    FIFTH 

NERVE. 

External  Portion.  Internal  Portion. 

To  temporal  muscle.  Auriculotemporal. 

—  masseter  Inferior  dental. 

—  external  pterygoid.  Gustatory  or  lingual. 

—  internal  pterygoid.  Mylo-hyoideus. 

—  buccal.  Anterior  belly  of  digastric. 

The  deep  temporal  branches,  two  in  number,  anterior  and  pos- 
terior, pass  outwards  close  to  the  great  wing  of  the  sphenoid 
bone,  and  ascend  with  the  temporal  arteries  to  the  temporal 
muscle.  A  middle  temporal  nerve  is  not  infrequently  present, 
and  ascends  beneath  the  temporal  muscle  to  enter  its  deeper 
aspect.  The  posterior  branch  is  occasionally  joined  with  the 
masseteric  nerve,  the  anterior  with  the  buccal  nerve. 

The  branch  to  the  w^/j-jtv/rr  runs  outwards  above  the  external 
pterygoid,  through  the  sigmoid  notch  of  the  mandible,  to  the 
under  surface  of  the  muscle. 

The  branch  of  the  external  pterygoid  con\cs,  apparently,  from 
the  buccal  nerve  in  its  passage  through  this  muscle. 

The  branch  to  the  internal  pterygoid  muscle  proceeds  from 
the  inner  side  of  the  main  trunk,  close  to  the  otic  ganglion,  and, 
descending  between  the  internal  pterygoid  and  the  tensor  palati, 
enters  the  inner  and  deeper  aspect  of  the  muscles. 


1^2 


INFERIOR    MAXILLARY    OR    MANDIBULAR    NERVE, 


The  buccal  branch,  a  sensory  nerve  united  at  its  origin  with 
the  anterior  deep  temporal  and  external  pterygoid  nerves,  passes 
either  above  or  between  the  fibres  of  the  external  pterygoid  to 
the  buccinator,  where  it  spreads  out  into  filaments,  which  form 


SZliSOPY  ROOT 


Fig.  S7 


a  plexus  with  the  buccal  branches  of  the  facial  nerve,  and  then 
supply  the  skin,  mucous  membrane,  and  glands  of  the  cheek 
with  common  sensation.  The  motor  power  of  the  buccinator, 
remember,  is  derived  from  the  facial  nerve.  That  this  buccal 
branch  is  mainly  scn.sory  is  proved  by  the  action  of  the  muscle 
still  continuing  when  the  motor  division  of  the  fifth  nerve  is 
paralyzed.  The  evidence  is  corroborated  by  a  case  in  which  this 
buccal  branch  proceeded  from  the  second  division  of  the  fifth 


INFERIOR    MAXILLARY    OR    MANDIBULAR    NERVE.  1 53 

nerve ;  no  communication  being  discovered,  after  very  careful 
dissection,  between  it  and  the  motor  root  of  the  third  division.* 

The  auriculo-tcvipoyal  branch  arises  by  two  roots  which  em- 
brace the  middle  meningeal  artery  before  if  enters  the  skull. 
The  nerve  runs  backwards  behind  the  external  pterygoid  and  the 
neck  of  the  mandible,  ascends  at  first  beneath  the  parotid  gland, 
then  over  the  root  of  the  zygoma  with  the  temporal  artery,  and 
divides,  like  it,  into  an  anterior  and  a  posterior  branch.  The 
posterior  branch  supplies  the  pinna  and  surrounding  tissues  ;  the 
anterior  is  distributed  to  the  skin  covering  the  vertex  and  tem- 
poral region,  communicating  with  the  temporal  branches  of  the 
facial  nerve  and  the  orbital  branch  of  the  maxillary. 

The  auriculo-temporal  communicates  at  its  origin  with  the 
otic  ganglion,  and  then  ascends  behind  the  mandible  with  the 
temporal  branches  of  the  facial  n.  ;  it  also  gives  off  an  articular 
brajicJi  to  the  temporo-mandibular  joint  ;  two  brandies  to  the 
meatus  auditorius  and  the  membrana  tympani ;  parotid  branches 
to  the  gland;  auricular  brandies,  two  in  number — 2in  inferior, 
which  is  distributed  to  the  ear  below  the  auditory  meatus,  and  a 
superior  to  the  tragus  and  auricle.  Its  branches  have  been 
described  (p.  23). 

The  inferior  dental  branch  emerges  beneath  the  external 
pterygoid,  and  descends  between  the  ramus  and  the  internal 
lateral  ligament  of  the  mandible  to  the  dental  foramen,  which 
it  enters  with  the  dental  or  mandibular  artery.  It  then  runs 
in  the  canal  in  the  diploe  of  the  mandible,  and  furnishes  fila- 
ments which  ascend  through  the  canals  in  the  fangs  of  the  teeth 
to  the  pulp  in  their  interior.  Opposite  the  foramen  mentale  it 
divides  into  two  branches,  the  mental  and  the  incisor.  Observe 
that  the  same  nerve  which  supplies  the  teeth  supplies  the  gums  ; 
hence  the  sympathy  between  them. 

a.  The  ;;/j/^-/^jf/V  branch,  apparently  arising  from  the  dental,  is  derived  from 
the  motor  root  of  the  fifth,  and  may,  with  careful  dissection,  be  traced  to  it. 
It  leaves  the  sheath  of  the  dental  nerve  near  the  foramen  in  the  mandible, 
and  runs  in  a  groove  on  the  inner  side  of  the  ramus  to  the  lower  surface  of  the 
mylo-hyoid,  which  muscle  it  supplies  together  with  the  anterior  portion  of  the 
digastric. 

b.  The  denial  branches  pass  upwards  to  the  fangs  of  the  molar  and  bicuspid 
teeth. 

c.  The  incisor  branch  is  the  continuation  of  the  nerve,  and  passes  to  the  svm- 
physis,  supplying  the  canine  and  incisor  teeth. 

d.  The  7Hciital  branch  (sometimes  called  labial)  emerges  through  the  foramen 

*  Turner,  "  On  the  Variation  of  the  Buccal  Nerve."  Journal  0/  Aiiat.  and  Phys.,  No.  I.,  1866. 


154 


GUSTATORY    NERVE. 


mentale,  and  soon  divides  into  numerous  branches  ;  some  ascend  to  the  lower  lip 
beneath  the  depressor  labii  inferioris,  and  communicate  with  the  facial  nerve  ;  others 
pass  inwards  to  the  skin  of  the  chin. 

The  gnstatoiy  or  Ihigiial  nerve  lies  at  first  behind  the  external 
pterygoid  m.,  then  descends  obliquely  forwards  between  the 
ramus  of  the  mandible  and  the  internal  pterygoid  m.,  and  sub- 
sequently for  a  short  distance  between  the  mandible  and  the 
superior  constrictor  of  the  pharynx.  Here  it  lies  close  under 
the  mucous  membrane  of  the  mouth  near  the  last  molar  tooth  of 
the  mandible.  Division  of  it  in  this  situation  relieves  pain  in 
cancer  of  the  tongue.  The  gustatory  n.  then  rests  upon  the 
stylo-glossus  and  the  hyo-glossus  m.,  and  af-ter  crossing  Whar- 
ton's duct  passes  to  the  tip  of  the  tongue. 

The  nerve  at  first  lies  in  front  of  the  mandibular  nerve  (with 
which  it  is  frequently  connected),  and  beneath  the  internal  max- 
illary a.  Beneath  the  external  pterygoid,  the  gustatory  n.  is 
joined  at  an  acute  angle  by  the  cJiorda  tympani  (a  branch  of  the 
facial).  This  branch  emerges  through  a  small  canal,  catial  of 
HugHier,  by  the  side  of  the  Gasserian  fissure,  and  passing  behind 
the  dental  n.,  meets  the  gustatory,  and  runs  along  the  lower 
border  of  this  nerve  to  supply  the  submandibular  gland  ;  part  of  it 
joins  the  submandibular  ganglion,  and  it  is  then  eventually  dis- 
tributed to  the  lingualis  muscle. 

The  gustatory  nerve  in  its  course  gives  off  — 

a.  Cof}itniiiiicaliHg  branches  to  the  hypoglossal  n.,  forming  two  or  more  loops 
at  the  anterior  border  of  the  hyo-glossui  muscle. 

b.  Co7)imu)iicati)i£;  brai/c/ws  to  the  submaxillary  ganglion. 

c.  Branc/ifs  to  the  mucous  viemb7-a}ie  of  the  mouth,  gums,  and  sublingual  gland. 

d.  Lingual  branches  which  pass  to  the  papillae  of  the  sides  and  tip  of  the 
tongue;  here  also  we  find  communications  between  this  nerve  and  the  hypo- 
glossal. 

The  duct  of  the  submaxillary  ox  submandibular  ^zx\i\.  (p.  109), 
Wharton  s  duct,  can  now  be  traced  to  its  termination.  It  passes 
from  its  under  surface,  runs  forwards  under  the  mylo-hyoideus 
and  upon  the  hyo-glossus  muscle  ;  it  then  passes  beneath  the 
gustatory  nerve,  and  subsequently  runs  between  the  sublingual 
gland  and  the  genio-hyo-glossus,  to  open  into  the  floor  of  the 
mouth,  by  the  side  of  the  fr^enum  linguaD.  Its  length  is  about 
two  inches  (5  ^;«.)  ;  its  dimensions  are  not  equal  throughout  ; 
it  is  dilated  about  the  middle,  and  contracted  at  the  orifice. 
Saliva,  collected  in  the  dilated  portion,  is  sometimes  spurted  to 
a  considerable  distance  out  of  the  narrow  orifice,  in  consequence 
of  the  sudden  contraction  of  the  nci":hborinfr  muscles. 


INTERNAL  LATERAL  LIGAMENT.  I  55 

The  gland  is  supplied  with  nerves  by  branches  from  the  sub- 
mandibular ganglion,  from  the  sympathetic,  and  the  mylo-hyoid 
nerves. 

In  the  floor  of  the  mouth  there  occasionally  exists  a  cystic 
tumor,  called  a  ramtla,  with  semi-transparent  walls,  perceptible 
beneath  the  tongue.  By  some  of  the  older  writers  it  was  looked 
upon  as  an  abnormal  dilatation  of  the  submandibular  duct. 
There  is,  however,  no  reason  for  believing  this  swelling  (except 
very  rarely)  to  be  connected  with  the  duct.  It  is  rather  a 
cyst  formed  in  the  loose  areolar  tissue  under  the  tongue,  or  is 
an  enlargement  of  one  of  the  small  bursae  which  normally  exist 
in  this  situation.  The  character  of  the  saliva  presents  no  agree- 
ment with  the  fluid  contained  in  these  cysts,  which  is  thickly 
glairy,  like  the  white  of  an  egg. 

Internal  Lateral  or  Spheno-mandibular  Ligament. — 
This  so-called  ligament  (which  is  more  like  a  layer  of  fascia) 
passes  from  the  spinous  process  of  the  sphenoid  bone  to  the 
inner  side  of  the  foramen  dentale.  Between  this  ligament  and 
the  neck  of  the  mandible  we  find  the  internal  maxillary  artery 
and  vein,  the  auriculo-temporal  nerve,  the  middle  meningeal 
artery,  the  mandibular  nerve  and  artery,  and  a  portion  of  the 
parotid  gland. 

At  this  stage  of  the  dissection  you  will  be  able  to  trace  the 
course  and  relations  of  the  internal  carotid  artery.  But  before 
•doing  this,  examine  the  several  objects  which  intervene  between 
the  external  and  internal  carotids.  These  are:  i.  The  stylo- 
glossus ;  2.  The  stylo-pharyngeus  ;  3.  The  glosso-pharyngeal 
nerve  ;  4.  The  stylo-hyoid  ligament. 

Stylo-glossus.  —  This  arises  from  the  front  of  the  styloid 
process  near  the  apex,  and  from  the  stylo-mandibular  ligament. 
It  passes  at  first  downwards  and  then  horizontally  forwards,  and 
is  inserted  along  the  side  of  the  tongue  as  far  as  the  tip,  some 
of  its  lower  fibres  decussating  with  those  of  the  hyo-glossus. 
Its  action  is  to  retract  the  tongue.  Its  ncive  is  a  branch  of  the 
hypoglossal. 

Stylo-pharyngeus.  —  This  arises  from  the  inner  side  of  the 
styloid  process  near  the  base,  and  is  inserted  into  the  upper  and 
posterior  edges  of  the  thyroid  cartilage.  It  descends  along  the 
side  of  the  pharynx  between  the  superior  and  the  middle  con- 
strictors ;  some  of  its  fibres  blend  with  the  constrictor  muscles  ; 
others  join  those  of  the  palato-pharyngeus  at  its  insertion. 
Curving  round  its  lower  border  is  seen  the  glosso-pharyngeal 


156 


GLOSS O-PHARYNGEAL    NERVE. 


nerve,  from  which  its  nerve-supply  is  derived.  Its  action  is  to 
raise  the  larynx  with  the  pharynx  in  deglutition.*     (See  Fig.  89.) 

Between  the  stylo-glossus  and  stylo-pharyngeus,  and  nearly 
parallel  with  both,  is  the  stylo-Jiyoid  ligament.  It  extends  from 
the  apex  of  the  styloid  process  to  the  lesser  cornu  of  the  os 
hyoides.     It  is  often  more  or  less  ossified. 

The  ascending  palatine  ai-teiy,  a  branch  of  the  facial  (p.  114), 


Fig.  58. 


runs  up  between  the  stylo-glossus  and  the  stylo-pharyngeus,  and 
divides  into  branches  which  supply  these  muscles,  the  palate,  the 
side  of  the  pharynx,  and  the  tonsils.  It  inosculates  with  the 
descending  palatine,  a  branch  of  the  internal  maxillary. 

Glosso-pharyngeal   Nerve.  —  The  glosso-pharyngeal  nerve 

*  Varieties  of  this  muscle  are  frequently  met  with,  chiefly  as  supernumerary 
muscles.  They  arise  variably  from  neif^hhoriiif;  parts  of  the  base  of  the  skull  close 
to  the  styloid  process,  and  are  inserted  either  into  tlie  pharyngeal  constrictors  or 
into  the  :iponeu-osis  of  the  pharynx. 


GLOSSO-PHARYNGEAL    NERVE.  I  57 

is  observed  curving  forwards  round  the  lower  border  of  the  stylo- 
pharyngeus  (p.  155).  It  is  the  ninth  cranial  nerve,  arises  by  five 
or  SIX  filaments  from  the  groove  between  the  olivary  body  and 
the  restiform  tract  of  the  medulla,  .leaves  the  skull  through  the 
middle  part  of  the  foramen  jugulare  in  a  separate  sheath  of 
dura,  in  front  of  the  pneumogastric  and  spinal  accessory  nerves, 
and  descends  between  the  internal  jugular  vein  and  the  internal 
carotid  artery.  It  then  crosses  in  front  of  the  artery  below  the 
styloid  process,  and  proceeds  along  the  lower  border  of  the 
stylo-pharyngcus.  At  this  point  it  curves  forwards  over  that 
muscle  and  the  middle  constrictor  of  the  pharynx,  and  disap- 
pears beneath  the  hyo-glossus,  where  it  divides  into  its  terminal 
branches,  which  supply  the  mucous  membrane  of  the  pharynx, 
the  back  of  the  tongue,  and  the  tonsils. 

-The  glosso-pharyngeal  is,  at  its  origin,  purely  a  sensory  nerve. 
But  soon  after  its  exit  from  the  skull  it  receives  communications 
from  the  facial,  the  pneumogastric,  and  the  sympathetic,  so  that 
it  soon  becomes  a  compound  nerve  —  i.e.,  composed  of  both  sen- 
sory and  motor  filaments.  At  the  base  of  the  skull  it  presents 
two  ganglia  —  \.\\q  jjignlar  {ganglio7i  of  EJirenritter),  which  has 
no  branches,  and  the  pctrons  (ganglion  of  Andersch).  The 
branches  given  off  by  the  petrous  ganglion  \vill  be  dissected 
hereafter ;  *  at  present  the  student  can  only  make  out  the 
branches  which  this  nerve  gives  off  in  the  neck,  namely :  — 

Carotid  branches,  which  surround  the  internal  carotid  artery  as  far  as  its  origin, 
and  communicate  with  the  pharyngeal  branch  of  the  pneumogastric  and  with  the 
sympathetic. 

Fharyugeal  branches,  three  or  four  in  number,  which  form  by  the  side  of  the 
middle  constrictor  of  the  pharynx,  a  plexus,  the  pharyngeal  plexus,  supplemented 
by  filaments  derived  from  the  pneumogastric,  the  nervus  accessorius,  the  external 
laryngeal,  and  the  sympathetic.  Its  branches  supply  the  constrictor  muscles  and 
the  mucous  m.embrane  of  the  pharynx,  the  back  of  the  tongue,  and  the  tonsils. 

Muscular  branches  which  enter  the  stylo-pharyngeus  m. 

Tonsillar  branches  which  are  given  to  the  soft  palate  and  the  fauces,  and  to  the 
tonsils  forming  a  plexus  [circulus  tonsillaris]. 

Lingual  branches,  two  in  rumber,  which  are  distributed  to  the  base  and  lateral 
aspects  of  the  tongue  :  one  branch  turns  upwards  and  is  distributed  to  the  papillae 
circumvallata;,  and  the  mucous  membrane  of  the  posteiior  third  of  the  tongue  as 
far  backwards  as  the  epiglottis;  the  other  passes  to  the  middle  of  the  side  of  the 
tongue  communicating  with  the  gustatory  nerve. 

The  Styloid  process  must  now  be  cut  through  at  its  base,  and 
turned  forwards  with  the  muscles  arising  from  it.  The  internal 
carotid  artery  will  thus  be  exposed  in  the  cervical  region,  as  far 

*  P.  274. 


158  INTERNAL  CAROTID  ARTERY. 

as  the  carotid  canal.  The  part  of  the  artery  contained  within 
the  carotid  canal  will  be  described  hereafter. 

Internal  Carotid  Artery.  — The  internal  carotid  artery  pro- 
ceeds from  the  bifurcation  of  the  common  carotid  at  the  upper 
border  of  the  thyroid  cartilage,  and  ascends  vertically  to  the 
base  of  the  skull  by  the  side  of  the  pharynx,  in  front  of  the 
transverse  processes  of  the  three  upper  cervical  vertebrae.  It 
enters  the  skull  through  the  carotid  canal  in  the  temporal  bone, 
runs  tortuously  by  the  side  of  the  body  of  the  sphenoid,  and 
terminates  in  branches  which  supply  the  orbit  and  the  brain. 
It  is  divided  into  four  portions  — the  cervical,  petrous,  cavern- 
ous, and  cerebral.  In  the  cervical  part  of  its  course  it  is  situ- 
ated immediately  to  the  outer  side  of  the  external  carotid  artery, 
behind  the  inner  border  of  the  sterno-mastoid.  It  soon  gets 
beneath  the  external  carotid,  and  lies  deeply  beneath  the  parotid 
gland,  and  ascends  by  the  side  of  the  pharynx.  It  lies  npon  the 
rectus  capitis  anticus  major,  the  superior  laryngeal  nerve,  and 
the  superior  cervical  ganglion  of  the  sympathetic ;  to  its  outer 
side  is  the  internal  jugular  vein  and  the  pneumogastric  nerve  ; 
to  its  inner  side  is  the  pharynx  ;  the  superior  constrictor  muscle 
separates  it  from  the  tonsil,  and  the  ascending  pharyngeal 
artery  ;  it  is  crossed,  successively,  by  the  hypoglossal  nerve,  the 
occipital  artery,  the  digastric,  and  stylo-hyoid,  muscles  ;  higher 
up  it  is  crossed  by  the  styloid  process,  the  stylo-glossus,  and 
stylo-pharyngeus  muscle,  by  the  glosso-pharyngeal  nerve  and  the 
stylo-hyoid  ligament,  all  of  which  last-named  structures  inter- 
vene between  it  and  the  external  carotid, 

The  most  important  relation  of  the  artery,  in  a  surgical  point 
of  view,  is  that  it  ascends  close  by  the  side  of  the  pharynx 
tonsil  *  In  opening  an  abscess,  therefore,  near  the  tonsil,  or  at 
the  back  of  the  pharynx,  be  careful  to  introduce  the  knife  with 
its  point  inwards  towards  the  mesial  line  ;  observe  this  caution 
the  more,  because  in  some  subjects  the  internal  carotid  makes  a 
curve,  or  even  a  complete  curl  upon  itself,  in  its  ascent  near  the 
pharynx.  In  such  cases  an  undue  deviation  of  the  instrument 
in  an  outward  direction  might  injure  the  vessel. 

Ascending     Pharyngeal    Artery.  —  This    artery   generally 

*  As  the  interval  between  the  artery  and  the  tonsil  is  considerable,  as  can  be 
shown  by  horizontal  section,  it  is  not  likely,  except  in  the  hands  of  a  bungling 
operator,  that  the  artery  can  be  punctured,  but  as  the  arterial  anastomoses  is  pro- 
fuse, considerable  haemorrhage  may  result  in  the  old  knife  operation  for  removal 
of  part  of  the  tonsil,  but  with  the  guillotine  this  is  avoided.  —  A.H. 


PNEUMOGASTRIC    NERVE. 


159 


arises  from  the  back  part  of  the  external  carotid  about  half  an 
inch  {12.^  run.)  above  the  angle  of  the  common  carotid.  It 
ascends  in  a  straight  course  between  the  internal  carotid  artery 
and  the  side  of  the  pharynx,  towards  the  base  of  the  skull,  rest- 
ing upon  the  rectus  capitis  anticus  major.  It  gives  off  three 
sets  of  branches : — 

a.  Pharyngeal  branches,  three  or  four  in  number:  the  two  lower  supply  the 
inferior  and  middle  constrictors,  and  stylo-pharyngeus,  anastomosing  with  the 
superior  thyroid  a. ;  the  upper  branch,  the  palatine,  ascends  upon  the  superior 
constrictor,  runs  down  with  the  levator  palati,  above  the  superior  constrictor,  and 
supplies  the  muscles  of  the  palate,  the  Eustachian  tube,  and  the  tonsil. 

b.  Frevertedral  branches,  which  supply  the  prevertebral  muscles,  the  superior 
cervical  ganglion  of  the  sympathetic,  the  lymphatic  glands,  and  the  pneumogastric 
and  hypoglossal  nerves. 

c.  Mc)ti>igcal  branches,  which  supply  the  dura;  passing  through  the  foramen 
lacerum  medium,  the  anterior  condylar  foramen,  and  the  foramen  jugulare  with 
the  internal  jugular  vein. 

Pneumogastric  Nerve  or  Tenth  N.  —  T\\& pneumogastric 
netve  is  the  tenth  cranial  nerve,  and  has  the  longest  course  of 
all  the  cerebral  nerves.  It  arises  from  the  medulla  by  a  series 
of  roots,  from  twelve  to  fifteen  in  number,  from  the  front 
of  the  restiform  body.  It  passes  out  of  the  skull  in  a  common 
sheath  of  dura  and  arachnoid,  with  the  nervus  aceessorius 
through  the  foramen  jugulare.  It  is  a  sensory  nerve  at  its 
commencement,  but  afterwards  is  a  mixed  n. 

Within  the  foramen  jugulare  a  small  ganglion — ganglion  of 
the  root  (Arnold's  ganglion)  —  about  one-sixth  of  an  inch  {^mm.) 
in  length,  is  situated  upon  the  pneumogastric  nerve,  and  is  joined 
by  a  branch  from  the  nervus  aceessorius.  This  ganglion  will  be 
described  hereafter.  About  half  an  inch  {12.^  vim)  below  the 
preceding  the  pneumogastric  nerve  swells  out,  and  forms  a  sec- 
ond ganglion — ganglion  of  the  trunk  —  (inferior  ganglion),  of 
a  reddish-gray  color.  This  ganglion  occupies  about  an  inch 
{2.^  cm)  of  the  nerve,  but  does  not  involve  the  whole  of  its 
fibres,  the  branch  from  the  spinal  accessory  joining  the  pneumo- 
gastric below  the  ganglion.  It  is  united  to  the  hypoglossal 
nerve,  from  which  it  receives  filaments ;  it  also  receives  fila- 
ments from  the  first  and  second  spinal  nerves,  and  from  the 
superior  cervical  ganglion  of  the  sympathetic. 

Thus,  the  pneumogastric,  at  its  origin  probably  a  nerve  of 
sensation  only,  becomes,  in  consequence  of  the  connecting  fila- 
ments from  these  various  branches,  a  compound  nerve,  and  in 
all  respects  analogous  to  a  spinal  nerve. 


l60  BRANCHES    OF    THE    PNEUMOGASTRIC    NERVE. 

Leaving  the  skull  at  the  foramen  jugulare,  the  nerve  descends 
in  front  of  the  cervical  vertebras,  lying  successively  upon  the 
rectus  capitis  anticus  major  and  the  longus  colli.  In  the  upper 
part  of  the  neck  it  is  situated,  lying  in  the  same  sheath,  between 
the  internal  carotid  artery  and  the  internal  jugular  vein  ;  lower 
down  it  lies  between  and  behind  the  common  carotid  and  the  in- 
ternal jugular  vein.  It  enters  the  chest  on  the  right  side,  cross- 
ing in  front  of  the  first  part  of  the  subclavian  artery,  nearly  at 
a  right  angle ;  on  the  left,  running  nearly  parallel  with  it. 

In  their  course  through  the  chest  the  pneumogastric  nerves 
have  not  similar  relations.  The  rigJit  nerve  lies  beneath  the 
subclavian  vein,  and  then  descending  behind  the  right  brachio- 
cephalic vein  by  the  side  of  the  trachea,  is  continued  behind  the 
right  bronchus  to  the  posterior  part  of  the  oesophagus.  The 
left  nerve  passes  behind  the  left  brachio-cephalic  vein,  then 
crosses  in  front  of  the  arch  of  the  aorta,  and  behind  the  left 
bronchus  to  the  anterior  part  of  the  oesophagus.  Both  nerves 
subdivide  on  the  oesophagus  into  a  plexus,  the  right  nerve  form- 
ing th.Q  paste j'ior  cesophageal  plexus,  the  left  the  anterior.  Each 
plexus  again  collects  its  fibres  together  to  form  a  single  trunk ; 
thus  two  main  nerves  are  formed  which  pass  with  the  oesophagus 
through  the  diaphragm  ;  of  these  the  right  is  distributed  over 
th2  posterior,  the  left  over  the  anterior  surface  of  the  stomach.* 

In  their  long  course  from  the  medulla  to  the  abdomen  the 
pneumogastric  nerves  supply  branches  to  most  important 
organs ;  namely,  to  the  pharynx,  the  larynx,  the  heart,  the 
lungs,  the  oesophagus,   the   stomach,   and  the  liver. 

The  branches  of  the  pneumogastric  are  those  of  communication  and  those  of 
distribution :  — 

1.  The  branches  of  comffiunication  are  those  in  connection  with  the  ganglion 
of  the  root  and  the  ga  iglion  of  the  trunli. 

a.  The  ganglion  of  the  root  has  connecting  filaments  with  the  accessory  por- 
tion of  the  spinal  acce.ssory,  the  superior  cervical  ganglion  of  the  sympathetic,  and 
with  the  petrous  ganglion  of  the  glossopharyngeal. 

b.  T\\&  ganglion  of  the  trunk  has  communicating  filaments  with  the  hypoglossal, 
th'i  loop  between  the  first  two  cervical  nerves,  and  the  superior  cervical  ganglion 
of  the  sympathetic. 

2.  The  branches  of  distribution  are  — 

a.  The  aiiriculir  (Arnold),  which  cannot  at  present  be  seen,  will  be  made  out 
in  the  dissection  of  the  nerve  at  the  base  of  the  skull. 

b.  The  pharyni^enl  arises  from  the  upper  part  of  the  ganglion  of  the  trunk, 
and,  receiving  a  filament  from  the  accessory  part  of  the  spinal  accessory,  descends 

*  The  difference  in  the  course  and  destination  of  the  right  and  the  left  pneu- 
mogastric nerves  may  be  explained  in  the  process  of  development.  The  student 
is  therefore  referred  to  works  which  treat  of  this  subject. 


PNEUMOGASTRIC    NERVE. 


i6i 


Fig.  59. 


■Apparent   Origin   and  Distribution  of  the  Glosso-pharyngeal,  Pneumogas 
TKic,  AND  Spinal  Accessory  Nerves. 


1,3,4.  Medulla,  i.  Ant.  p\Tamid.  3.  Olivary  body.  4.  Restiform  body.  2.  Pons.  5.  Seventh 
or  facial.  6.  Origin  of  the  glosso-pliaryngeal.  7.  Ganglion  of  Andersch.  8.  Trunk  of  the 
nerve.  9.  Spinal  accessory  nerve.  10.  Superior  or  ganglion  of  the  root  of  the  pneuniogastric 
nerve.  11.  Inferior  or  ganglion  of  the  trunk.  12.  Trunk.  13.  Pharyngeal  branch  forming 
pharyngeal  plexus  ( 14),  assisted  by  a  branch  from  the  glosso-pharyngeal  (Ji),  and  one  from  the 
superior  l.ir\Tigeal  nerve  (15).  16.  Cardiac  branches.  17.  Recurrent  laryngeal  branch.  18.  An- 
terior pulmonary  and  cardiac  branches.  19.  Posterior  pulmonary  and  cardiac  branches. 
20.  CEsophageal  plexus.  21.  Ga'-tric  branches.  22.  Origin  of  the  spinal  portion  of  the  spinal 
accessory  nerve.  23.  Branches  of  the  whole  nerve  to  sterno-mastoid  muscle.  24.  iiranches 
to  the  trapezius. 


1 62  SPINAL    ACCESSORY    NERVE. 

either  in  front  of  or  behind  the  internal  carotid.  The  nerve,  after  passing  to  the 
inner  side  of  the  internal  carotid,  divides  into  branches,  which  with  the  other  fila- 
ments (described  p.  157)  upon  the  middle  constrictor  muscle  form  the  pharyngeal 
plexus.  From  this  plexus  branches  are  distributed  to  the  muscles  and  the  mucous 
membrane  of  the  pharynx* 

c.  The  superior  laryngeal,  derived  from  the  middle  of  the  ganglion  of  the 
trunk,  descends  behind  the  internal  carotid,  and  divides  into  two  branches,  the 
internal  and  the  external  laryngeal. 

The  internal  laryngeal  passes  to  the  interval  between  the  os  hyoides  and  the 
thyroid  cartilage,  and  enters  the  larynx  (with  the  superior  laryngeal  a.),  through 
the  thyro--hyoid  membrane,  to  be  distributed,  as  a  nerve  of  sensation,  to  the 
mucous  membrane  of  the  larynx  and  epiglottis.  The  external  laryngeal,  the 
smaller,  gives  off  some  branches  to  the  pharyngeal  plexus,  the  inferior  constrictor, 
and  the  thyroid  body,  and  then  descends  by  the  side  of  the  la  ynx  beneaLh  the 
depressors  of  the  os  hyoides  to  supply  the  cricothyroid  muscle;  it  communicates 
with  the  superior  cardiac  nerve  of  the  sympathetic. 

d.  The  ce)"vical  cardiac  brandies  descend  behind  the  sheath  of  the  carotid 
artery  to  the  cardiac  plexus.  The  tipper  branches,  one  or  two  in  number,  are 
small,  and  proceed  from  the  ganglion  of  the  trunk ;  they  join  the  cardiac  branches 
of  the  sympathetic  and  the  deep  cardiac  plexus  ;  the  lower  comes  from  the  trunk 
of  the  pneumogastric  before  it  enters  the  chest.  Subsequently,  the  right  lower 
cardiac  nerve  descends  by  the  side  of  the  innominate  artery  to  join  the  deep  car- 
diac plexus ;  the  left  passes  over  the  arch  of  the  aorta  to  join  ,the  superficial 
cardiac  plexus. 

c.  The  inferior  or  recurrent  laryjigeal  7ierve  turns,  on  the  right  side,  under  the 
subclavian  artery  (p.  129),  and  ascends  obliquely  inwards  to  the  larynx  behind 
the  common  carotid  and  the  inferior  thyroid  arteries  ;  it  lies  subsequently  in  the 
groove  between  the  oesophagus  and  the  trachea.  On  the  left  side,  it  turns  under 
the  arch  of  the  aorta,  just  on  the  outer  side  ot  the  remains  of  the  ductus  arterio- 
sus ;  after  which  it  runs  up  between  the  trachea  and  the  oesophagus.  On  both 
sides  the  nerves  enter  the  larnyx  beneath  the  lower  border  of  the  inferior  constric- 
tor, and  supply  all  the  intrinsic  muscles  of  the  larynx  except  the  crico-thyroid. 
These  nerves,  as  they  turn  under  their  respective  vessels,  give  off  cardiac  branches 
to  the  deep  cardiac  plexus.  They  supply  also  filaments  to  the  trachea,  oesophagus, 
and  inferior  constrictor  muscle. 

The  remaining  branches  of  the  pneumogastric  nerve  to  the 
lungs,  heart,  oesophagus,  and  stomach  will  be  examined  in  the 
dissection  of  the  chest. 

Spinal  Accessory  Nerve,  or  Eleventh  N.  —  The  spinal 
accessory  nerve  issues  through  the  middle  part  of  the  foramen 
jugulare,  in  a  sheath  of  dura  common  to  it  and  the  pneumo- 
gastric nerve.  It  is  a  motor  nerve,  for  the  most  part  deriving 
its  small  sensory  and  also  some  motor  element  from  its  vagal 
or  accessory  or  Obertsciner  filaments  in  the  medulla.  (A.  H.) 
It  arises  by  numerous  filaments  from  the  side  of  the  medulla 
below  the  pneumogastric,  and  from  the  lateral  column  of  the 
spinal  cord  as  low  down  as   the   sixth   cervical  vetebra.     The 

*  A  branch  from  the  plexus  is  described  by  Tuschka  as  receiving  filaments 
from  the  pharyngeal  branches  of  the  glosso-pharyngeal  and  pneumogastric  nerves, 
and  joining  witii  the  hypoglossal  as  it  winds  round  the  occipital  artery. 


HYPOGLOSSAL    NERVE.  I 63 

filaments  which  arise  from  the  medulla  join  to  form  the  ac- 
cessory portion  of  the  nerve  ;  the  spinal  filaments  ascend  be- 
tween the  ligamentum  denticulatum  and  the  posterior  roots  of 
the  cervical  spinal  nerves,  and  form  the  spinal  poi-tion  of  the 
nerve.  These  portions  converge  to  the  jugular  foramen,  where 
they  commmiicate  with  each  other  more  or  less,  and  are  then 
continued  onwards  below  the  jugular  foramen  as  two  portions 
—  the  internal  or  accessory,  which  joins  the  pneumogastric  n.  ; 
the  external  or  spinal,  which  is  distributed  to  muscles. 

The  accessory  part,  within  the  foramen  jugulare,  sends  one  or 
more  filaments  to  the  ganglion  of  the  root  of  the  pneumogastric. 
It  lies  close  to  the  pneumogastric  nerve  at  the  ganglion  of  the 
trunk,  and  is  finally  incorporated  with  the  nerve  below  the  gan- 
glion. It  sends  filaments  to  the  pharyngeal  and  superior  laryn- 
geal branches  of  the  pneumogastric. 

The  spi?tal  part  separates  from  the  accessory  part  below  the 
foramen  jugulare.  It  then  takes  a  curved  course  backwards  and 
outwards,  lying  in  front  of  the  internal  jugular  vein  and  the 
transverse  process  of  the  atlas,  and  behind  the  digastric  and 
stylo-hyoid  muscles.  It  pierces  the  upper  part  of  the  sterno- 
mastoid  muscle  accompanied  by  the  superior  sterno- mastoid 
artery,  a  branch  of  the  occipital,  and  supplies  the  muscle,  joining 
in  its  substance  with  branches  from  the  third  cervical  n.  The 
nerve  then  crosses  obliquely  the  occipital  triangle,  where  it  com- 
municates with  the  second  and  third  cervical  nerves.  It  is  even- 
tually distributed  to  the  under  aspect  of  the  trapezius,  where  it 
is  joined  by  branches  from  the  third  and  fourth  cervical  nerves. 

Hypoglossal  Nerve.  —  The  apparent  origin  of  this  nerve  is 
by  from  ten  to  fifteen  filaments,  from  the  groove  between  the 
anterior  pyramid  and  the  olivary  body.  It  passes  through  the 
dura  in  two  fasciculi,  which  emerge  from  the  skull  through 
the  anterior  condylar  foramen,  and  then  unite  to  form  a  single 
nerve.  It  comes  forward  between  the  internal  jugular  vein  and 
the  internal  carotid  artery,  where  it  is  intimately  connected  with 
the  pneumogastric  nerve.  Its  further  course  has  been  described 
(p.  118). 

In  the  anterior  condylar  foramen  the  hypoglossal  gives  off  a 
small  filament  to  the  diploe  and  to  the  dura  around  the  foramen 
magnum.  At  the  base  of  the  skull  it  gives  off  several  branches, 
which  connect  it  with  the  ganglion  of  the  trunk  of  the  pneumo- 
gastric-nerve.  These  two  nerves  are  sometimes  almost  insepa- 
rably united.     It  gives  off  also  several  delicate  filaments  to  the 


164  SYMPATHETIC    NERVE    IN    THE    NECK. 

superior  cervical  ganglion  of  the  sympathetic,  and  communicates 
with  the  loop  formed  by  the  first  two  spinal  nerves  in  front  of 
the  atlas. 

Sympathetic  Nerve.  —  Now  examine  the  cervical  ganglia 
of  the  sympathetic  system  of  nerves.  This  system  consists  of  a 
series  of  ganglia  arranged  on  each  side  of  the  spine,  from  the 
first  cervical  to  the  last  sacral  vertebra.  The  successive  ganglia 
of  the  same  side  are  connected  by  intermediate  nerves,  so  as  to 
form  a  continuous  cord  on  each  side  of  the  spine  ;  this  consti- 
tutes what  is  called  the  trunk  of  the  sympathetic  system,  and  is 
connected  with  all  the  spinal  nerves.  Its  upper  or  cephalic 
extremity  enters  the-  cranium  through  the  carotid  canal,  sur- 
rounds the  internal  carotid  artery,  communicates  with  the  third, 
fourth,  fifth,  and  sixth  cranial  nerves,  and  joins  its  fellow  of  the 
opposite  side  upon  the  anterior  communicating  artery.*  Its 
sacral  extremity  joins  its  fellow  by  means  of  the  little  ganglion 
impar,  situated  in  the  mesial  line,  upon  the  cocyx. 

The  ganglia  are  connected  together  by  branches  composed  of 
gray  and  white  nei-ve  fibres  ;  they  are  also  connected  with  the 
spinal  nerves  by  two  filaments  —  one,  of  white  nerve-fibres,  which 
passes  from  the  spinal  nerve  to  the  ganglion  ;  the  other,  of  gray, 
from  the  ganglion  to  the  spinal  nerve.  Branches  of  distribution 
are  also  given  off  by  the  ganglia,  some  to  the  various  blood- 
vessels and  viscera,  forming  intricate  plexuses  upon  them  ; 
others  to  the  various  ganglia  of  the  viscera  —  the  cardiac  and 
semilunar  ganglia. 

The  different  portions  of  the  sympathetic  gangliated  cord  re- 
ceive, respectively,  the  distinguishing  names  of  the  cervical, 
thoracic,  lumbar,  sacral,  and  coccygeal.  At  present  we  have 
only  to  consider  the  cervical  portion  of  it. 

To  expose  the  cervical  ganglion  of  the  sympathetic,  the  inter- 
nal carotid  artery,  the  pneumogastric,  glosso-pharyngeal,  and 
hypoglossal  nerves  should  be  cut  through,  near  the  base  of  the 
skull ;  then  by  careful  dissection  the  superior  cervical  ganglion 
can  be  traced  out. 

Cervical  Ganglia  of  Sympathetic.  —  In  the  cervical  portion 
of  the  sympathetic  are  three  ganglia,  named  from  their  position, 
superior,  middle,  and  inferior. 

The  superior  cervical  ganglion,  the  largest  of  the  three,  is 
situated  near  the  base  of  the  skull,  opposite  the  second  and  third 

*  Here  is  silualed  the  so-called  ^'aw^Z/w/ ^y/iV^fj'. 


SYMPATHETIC  NERVE  IN  THE  NECK.  165 

cervical  vertebrae,  upon  the  rectus  capitis  anticus  major,  and  lies 
behind  and  on  the  inner  side  of  the  internal  carotid  artery.  It 
is  of  a  reddish-gray  color  like  the  other  ganglia,  of  an  elongated 
oval  shape,  varying  in  length  from  one  to  two  inches  (2.^  to ^  cm.). 
To  facilitate  the  description  of  its  several  branches,  we  divide 
them  into  an  upper,  a  lower,  an  external,  an  internal,  and  an 
anterior  set  — 

a.  Its  upper  or  cranial  branch  runs  with  the  internal  carotid  a.  into  the  carotid 
canal  of  the  temporal  bone,  and  there  divides  into  two  branches,  an  outer  and  an 
inner.  The  outer  and  larger  branch  accompanies  the  artery  through  its  bony 
canal,  ramifies  upon  it  by  the  side  of  the  body  of  the  sphenoid,  and  so  constitutes 
the  "Carotid  Plexus."*  P'rom  this  outer  branch  a  filament  proceeds  to  the 
Gasserian  ganglion;  another  to  the  sixth  cranial  nerve;  a  third  joins  the  great 
petrosal  branch  of  the  facial,  and  forms  the  Vidian  nerve,  and  thus  communicates 
with  the  spheno  palatine  ganglion.  It  also  communicates  in  the  carotid  canal 
with  the  tympanic  branch  of  the  glossopharyngeal.  The  inner  branch,  running 
on  with  the  artery  to  the  cavernous  sinus,  there  forms  another  ple.xus,  called  from 
its  position  the  "  Cavernous  Plexus."  Here  the  sympathetic  is  seen  to  commu- 
nicate with  the  third,  the  fourth,  and  the  ophthalmic  branch  of  the  fifth  and  sixth 
cranial  nerves,  and  with  the  ophthalmic  ganglion.  Lastly,  from  both  these  plex- 
uses secondary  plexuses  proceed,  of  which  the  minute  filaments  ramify  on,  and 
supply  the  coats  of,  the  terminal  branches  of  the  internal  carotid. 

b.  The  lower  branch  descends  and  joins  the  middle  cervical  ganglion  of  the 
sympathetic. 

c.  The  external  branches  are  numerous,  and  connect  the  ganglion  with  the 
ganglion  of  the  pneumogastric  and  hypoglossal  nerves,  and  with  the  four  upper 
cervical  spinal  nerves.  A  small  twig  also  joins  the  petrossal  ganglion  of  the 
glossopharyngeal  and  the  upper  ganglion  of  the  pneumogastric  in  the  foiamen 
jugulare. 

d.  The  internal  branches  are  distributed  to  the  pharynx,  larynx,  and  the  heart. 
The  pharyngeal  branches  join  the  pharyngeal  plexus  on  the  middle  constrictor  of 
the  pharynx;  the  laryngeal  join  the  superior  laryngeal  nerve;  the  cardiac  nerves, 
one  or  more  in  number  —  superior  cardiac  —  descend  behind  the  sheath  of  the 
carotid  in  front  of  the  inferior  thyroid  artery  and  recurrent  laryngeal  nerve,  and, 
entering  the  chest,  join  the  superficial  and  deep  cardiac  plexuses. 

e.  The  anterior  branches  lie  in  front  of  the  e.xternal  carotid  artery  and  ramify 
around  this  vessel  and  its  branches,  forming  the  various  plexuses,  and  named,  on 
account  of  their  delicacy,  the  nervi  molles.  In  some  of  these  plexuses  are  occa- 
sionally seen  several  ganglia,  the  intercaroticA  lingual,  temporal,  and  pharyngeal 
ganglia.  They  are  connected  with  the  several  ganglia  about  the  head  and  neck; 
namely,  the  ophthalmic,  spheno-palatine,  otic,  and  submaxillary  or  submandibular. 

The  middle  cervical  ganglion,  the  smallest  of  the  three  gan- 
glia, is  something  less  than  a  barleycorn  in  size.  It  is  situated 
behind  the  carotid  sheath,  about  the  fifth  or  sixth  cervical  verte- 
bra on  or  near  the  inferior  thyroid  artery. 

*  A  small  ganglion,  the  carotid  ganglion,  is  sometimes  met  with  in  this  plexus 
on  the  under  aspect  of  the  artery. 

t  Situated  in  the  angle  at  the  bifurcation  of  the  common  carotid  into  the  e.\- 
ternal  and  internal  carotid  arteries  ;  it  corresponds  in  structure  with  the  coccygeal 
gland. 


1 66 


SYMPATHETIC    NERVE    IN    THE    NECK. 


a.  It  is  connected  by  branches  with  the  superior  ganglion  above,  and  with  the 
inferior  cervical  ganglion  below. 

b.  Its  external  branches  usually  pass  outwards  to  join  the  fifth  and  sixth  cervi- 
cal spinal  nerves. 

c.  Its  internal  branches  are  distributed  to  the  thyroid  body  and  the  heart. 
The  branches  to  the  thyroid  body  accompany  the  inferior  thyroid  artery,  and  join 
the  superior  cardiac  nerve,  and  in  the  gland  they  communicate  with  the  external 


N   to  gre^' 

petrosal 
N.  to  lesser 
petrosal. 
N.  to  Eusta- 
chian tube 
Ns.  to  carotid 
plexus. 
Chorda  tympani. 


N   to  stylo- 
hyoid. 

N    to  dig3stric. 
Petrous 
ganglion. 

Carotid  plexus. 

Branch  to  phar- 
yngeal plexus. 
Lingual  branch. 


Ganglion 
trunk. 


<f   the 


Pharyngeal  n. 


Superior 
laryngeal. 


Gangliform  en- 
largement. 

N.  to  fenestra 
ovalis. 

N.  to  fenestra 
rotunda. 

Tympanic  n. 


Auricular  n. 

Glosso- 
pharyngeal n. 

Jugular  ganglion 
of  do. 

Pneumogastric. 
Ganglion  of  root. 


Spinal  accessory. 


Hypoglossal. 

Supr.  cervical 

ganglion, 
ist  cervical  n. 
Br.  to  ganglion 

of  trunk. 

2od  cervical  n. 


Fig  6o.  —  Diagram  OF  the  Communications  op  the  Facial  Glosso-pharvngkal,  Pneumo- 
GASTKic,  Spinal,  Accessory,  Hypoglossal.  Sympathetic  and  the  Two  Upper  Cer- 
vical Nerves. 

I.  Great  petrosal  nerve.  2.  Lesser  petrosal  nerve.  3.  External  petrosal  nerve.  4.  Nerve  to 
Stapedius  muscle.     5.    Spheno-palatine  ganglion.    6.   Otic  ganglion. 


and  recurrent  laryngeal  nerves.  The  middle  cardiac  nerz'e,  the  largest  of  the  three 
cardiac  nerves,  descends,  on  the  right  side  behind  the  common  carotid  a.,  usually 
in  front  of  the  first  part  of  the  subclavian  artery,  into  the  chest,  when  it  lies  on 
the  trachea.  It  is  joined  by  some  cardiac  filaments  from  the  recurrent  larnygeal 
nerve  and  superior  cardiac  nerve,  and  joins  the  deep  cardiac  plexus.  On  the  left 
side  this  cardiac  nerve  enters  the  chest  between  the  left  carotid  and  subclavian 
arteries. 


DISSECTION    OF    THE    THORAX.  1 6/ 

In  cases  where  the  middle  cervical  ganglion  is  absent,  the  pre- 
ceding nerves  are  supplied  by  the  sympathetic  cord  connecting 
the  superior  and  inferior  ganglia. 

The  inferior  ceitncal  ganglion  is  of  considerable  size,  and  is 
situated  in  the  interval  between  the  base  of  the  transverse  pro- 
cess of  the  seventh  cervical  vertebra  and  the  neck  of  the  first 
rib,  immediately  behind  the  vertebral  artery,  and  to  the  inner 
side  of  the  superior  intercostal  artery.  Not  infrequently  it  is 
coalesced  with  the  first  thoraic  sympathetic  ganglion. 

Its  branches  are  as  follows  :  — 

a.  Superior  branches  which  pass  upwards  and  connect  it  with  the  middle  cervi- 
cal ganglion. 

b.  Inferior  branches  which  descend,  some  in  front  of,  and  some  behind,  the 
subclavian  a.,  to  join  the  first  thoracic  ganglion.  One  of  these,  the  inferior  cardiac 
nerve,  passes  behind  the  subclavian  a  in  front  of  the  trachea,  to  join  the  deep 
cardiac  plexus,  beneath  the  arch  of  the  aorta,  and  communicates  with  the  recur- 
rent laryngeal  and  middle  cardiac  nerves. 

c.  External  branches  which  communicate  with  the  seventh  and  eighth  cervical 
nerves-;  others  form  a  plexus  around  the  vertebral  artery,  which  join  W"ith  the 
fourth,  fifth,  and  sixth  cervical  nerves. 


DISSECTION    OF   THE    THORAX. 

Before  the  several  organs  contained  in  the  thorax  are  exam- 
ined, the  student  should  have  some  knowledge  of  its  framework. 
The  ribs  with  their  cartilages  describe  a  series  of  arcs  increasing 
in  length  from  above  downwards,  and  form,  with  the  thoracic 
vertebrae  behind  and  the  sternum  in  front,  a  barrel  of  a  conical 
shape,  broader  in  the  lateral  than  in  the  antero-posterior  diam- 
eter. The  spaces  between  the  ribs  are  occupied  by  the  inter- 
costal muscles.  In  each  intercostal  space  there  are  two  layers 
of  these  muscles,  arranged  like  the  letter  X.  The  fibres  of  the 
outer  layer  run  obliquely  from  above  downwards  and  forwards  ; 
those  of  the  inner  layer  in  the  reverse  direction.  The  base  is 
closed  in  the  recent  state  by  a  muscle  —  the  diaphragm  —  which 
forms  a  muscular  partition  between  the  chest  and  the  abdomen. 
This  partition  is  arched  upwards,  so  that  it  constitutes  a  vaulted 
floor  for  the  chest,  and  by  its  capability  of  alternately  falling  and 
rising,  it  increases  and  diminishes  the  capacity  of  the  thorax. 

In  front,  the  diaphragm  is  attached  to  the  ensiform  cartilage, 
but  it  slopes  posteriorly,  to  become  attached  to  the  last  rib.  The 
circumference  of  the  diaphragm  is  convex  and  muscular  ;  in  the 
centre  it  is  flattened  and  aponeurotic.     On  the  right  side  it  cor- 


1 68  DISSECTION    OF    THE    THORAX. 

responds,  in  front,  with  the  upper  border  of  the  cartilage  of  the 
fifth  rib  ;  on  the  left  side  it  corresponds  with  the  upper  border 
of  the  sixth  rib. 

The  upper  opening  of  the  osseous  thorax  is  bounded  posteri- 
orly by  the  body  of  the  first  thoraic  vertebra,  laterally  by  the  first 
ribs,  and  in  front  by  the  upper  border  of  the  manubrium  sterni.* 

Such,  in  outline,  is  the  framework  of  the  thorax,  which  con- 
tains the  heart  Wiith  its  large  vessels  and  the  lungs.  Its  walls 
are  composed  of  different  structures  —  bone,  cartilage,  muscles, 
and  ligaments,  which  fulfil  two  important  conditions:  ist,  by 
their  solidity  and  elasticity  they  protect  the  important  organs 
contained  in  the  thorax  ;  2ndly,  by  their  alternate  expansion  and 
contraction  they  act  as  mechanical  powers  of  respiration.  For 
they  can  increase  the  capacity  of  the  chest  in  three  directions : 
in  height,  by  the  descent  of  the  diaphragm  ;.  in  width,  by  the 
rotation  of  the  ribs;  and  in  depth,  by  the  elevation  of  the 
sternum. 

The  chest  of  the  female  differs  from  that  of  the  male  in  the 
following  points  :  Its  general  capacity  is  less  ;  the  sternum  is 
shorter;  the  upper  opening  is  larger  in  proportion  to  the  lower  ; 
the  upper  ribs  are  more  movable,  and  therefore  permit  a  greater 
enlargement  of  the  chest  at  its  upper  part,  in  adaptation  to  the 
condition  of  the  abdouen  during  pregnancy. 

The  upper  opening  of  the  tJiotax  gives  passage  to  the  trachea, 
the  oesophagus,  the  large  vessels  of  the  head  and  neck  and  upper 
extremities,  viz.,  the  innominate,  the  left  carotid,  and  subclavian 
arteries,  with  the  left  innominate  and  right  subclavian  and  inter- 
nal jugular  veins,  the  superior  intercostal  and  internal  mammary 
arteries,  the  inferior  thyroid  veins,  the  sterno-hyoid,  sterno-thy- 
roid,  and  longus  colli  muscles  of  each  side,  the  pneumogastric, 
the  left  recurrent  laryngeal,    the  phrenic,  and  the  sympathetic 

*  That  the  student  may  have  some  knowledge  of  the  diameters  of  the  chest  at 
different  situations,  the  following  measurements  have  been  taken  from  a  well- 
articulated  male  skeleton  of  the  average  height :  The  anteroposterior  diameter  at 
the  uppar  opening  of  the  thorax  is  2\  inches  (5.6  ctn^,  at  the  articulation  of  the 
manubrium  with  the  gladiolus  it  is  \\  inches  (//.^  c///.),  and  at  the  junction  of  the 
gladiolus  with  the  ensiform  cartilage  it  has  increased  to  5!  (14-23  cm.)  inches. 
The  transverse  diameter  ot  the  upper  opening  was  found  to  be  4?  inches  (//  cm.)  \ 
between  the  second  ribs,  7  inches  [ly.^  cm)  ;  between  the  third,  8J  inches  (20.3 
cm.) ;  the  diameter  increased  in  regular  proportion  as  far  as  the  ninth  rib,  where  it 
attained  a  measurement  of  loe  inches  [26.6  cm)  ;  below  this  it  gradually  decreased. 
The  upper  border  of  the  manubrium  corresponds  to  the  second  thoracic  vertebra. 
The  articulation  of  the  manubrium  and  the  gladiolus  is  on  a  level  with  the  fourth 
thoracic  vertebra;  and,  lastly,  the  junction  of  the  en.siform  cartilage  with  the 
gladiolus  is  on  a  level  with  the  border  of  the  ninth  or  tenth  thoracic  veftebra. 


DISSECTION    OF    THE    THORAX.  1 69 

nerves  ;  the  cardiac  branches  of  the  sympathetic,  and  the  cardiac 
branches  of  the  pneumogastric ;  also  to  the  anterior  branch  of 
the  first  thoracic  nerve  as  it  passes  up  to  join  the  brachial  plexus, 
the  thoracic  duct,  the  thymus  gland  (in  early  life),  and,  lastly, 
to  the  apices  of  the  lungs,  which,  with  their  pleural  covering,  rise 
up  on  each  side  into  the  neck  for  about  one  inch  and  a  half 
{3-75  ^^'^•)  above  the  clavicle  ;  the  interspaces  between  these 
various  structures  being  occupied  by  a  dense  fibro-cellular  tissue, 
continuous  with  the  deep  cervical  fascia. 

The  diaphragm,  which  forms  the  base  of  the  thorax,  is  pierced 
by  the  following  foramina  :  The  aortic  of  cuing,  for  the  passage 
of  the  aorta,  vena  azygos  major,  thoracic  duct ;  the  cesopJiageal 
opening  for  the  oesophagus,  pueumogastric  nerves,  and  oesopha- 
geal branch  of  the  coronaria  ventriculi  artery  ;  the  foravictt 
quadratnniy  for  the  vena  ca\a  inferior,  a  branch  of  the  right 
phrenic  nerve  and  lymphatics  from  the  liver ;  the  right  cms 
transmits  the  greater  and  lesser  splanchnic  nerves  ;  the  left  cms, 
in  addition,  transmits  the  vena  azygos  minor.  In  front  there  are 
the  narrow  intervals  for  the  passage  of  the  internal  mammary 
arteries. 

Dissection.*  —  An  opening  must  be  made  into  the  chest  by 
carefully  removing  the  upper  four-fifths  of  the  sternum,  and  the 
cartilages  of  all  the  true  ribs.f  In  doing  this,  care  must  be 
taken  not  to  wound  the  pleura,  which  is  closely  connected  with 
the  cartilages.  On  one  side  the  internal  mammary  artery  should 
be  dissected  ;  on  the  other  removed. 

In  the  erect  position  the  apex  of  the  heart  pulsates  between 
the  fifth  and  sixth  ribs,  two  inches  below  the  left  nipple  and  one 
inch  to  its  sternal  side.  In  deep  respiration  it  may  descend  half 
an  inch. 

The  relation  of  the  chief  cardip-C  orifices,  one  to  the  other  and 
to  the  chest  wall,  is  as  follows  :  — 

I.  The  pulmonary  semilunar  valves  are  anterior  in  position  to 
the  aortic,  and  are  placed  behind  the  junction  of  the  third  costal 
cartilage  with  the  sternum  on  the  left  side. 

*  The  student  is  advised  in  making  the  dissection  of  the  thorax  to  introduce 
large  hat-pins  (similar  to  those  used  by  ladies  in  fastening  the  hat  to  the  hair  of 
their  heads)  to  outline  the  position  of  the  heart  before  removing  the  anterior  chest 
wall.  —  A.  H 

t  Those  who  a-e  more  proficient  in  d'ssection  should  not  remove  the  whole  of 
the  sternum,  but  leave  a  quarter  of  an  inch  of  its  upper  part  with  the  first  rib 
attached  to  it.  This  portion  serves  as  a  valuable  landmark,  although  it  obstnicts, 
to  a  certain  extent,  the  view  of  the  subjacent  vessels. 


I/O 


DISSECTION    OF    THE    THORAX. 


2.  The  aortic  semilunar  valves  are  more  deeply  placed  than 
the  pulmonary  semilunar  valves,  and  lie  behind  the  third  inter- 
costal space  close  to  the  left  side  of  the  sternum. 

3.  The  tricuspid  valves  lie  behind  the  sternum,  and  on  the 
middle  line  and  between  the  junction  of  the  fourth  costal  carti- 
lages with  the  sternum. 


Fig.  61.  —  Showing   the   Position    of   the  Heart  and  its  Valves   in   Rri.ation   to   the 
Chest  Walls.     (After  Mokkis.) 

4.  The  mitral  valves  (deepest  of  all)  lie  behind  the  third  inter- 
costal space,  about  an  inch  to  the  left  of  the  sternum. 

These  valves  are  so  situated  that  the  mouth  of  an  ordinary- 
sized  stethoscope  will  cover  a  portion  of  them  all,  if  placed  over 
the  sternal  end  of  the  third  intercostal  space  on  the  left  side. 


INTERNAL    MAMMARY    ARTERY.  I7I 

In  order  to  auscult  them  separately,  it  is  found  that  the  aortic 
valve  sound  is  best  heard  over  the  second  intercostal  space  at 
the  right  border  of  the  sternum.  The  pulmonary  valve  sound 
is  over  the  second  intercostal  space  at  the  left  border  of  the 
sternum.  The  tricuspid  valve  sound  is  over  the  middle  of  the 
sternum  above  the  ensiform  cartilage.  The  mitral  valve  sound 
is  best  heard  over  the  apex  of  the  heart.  A  circle  two  inches  in 
diameter  made  around  a  point  midway  between  the  left  nipple 
and  the  end  of  the  sternum  will  define  sufficiently  for  all  prac- 
tical purposes  that  part  of  the  heart  which  lies  immediately  be- 
hind the  wall  of  the  chest  and  is  not  covered  by  lung  or  pleura. 

In  the  dissection  of  the  chest  let  us  take  the  parts  in  the  fol- 
lowing order  :  — 

1.  Triangulans  stenii,  with  the  internal  mammary  artery. 

2.  Mediastina,  anterior,  middle,  posterior,  and  superior. 

3.  Pleura. 

4.  Position  and  form  of  the  lungs. 

5.  Pericardium. 

6.  Position  and  relations  of  the  heart. 

7.  Posterior  mediastinum  and  its  contents ;  namely,  the  aorta,  the  thoracic 

duct,  the  vena  azygos,  the  oesophagus,  and  pneumogastric  nerves. 

8.  Right  and  left  brachio  cephalic  veins  and  superior  vena  cava. 

9.  Course  of  the  phrenic  nerves. 

10.  Course  and  relations  of  the  arch  of  the  aorta. 

11.  The  three  great  branches  of  the  arch. 

12.  Sympathetic  nerve. 

13.  Intercostal  muscles,  vessels,  and  nerves. 

14.  Nerves  of  the  heart ;  cardiac  plexuses. 

Triangularis  Sterni.  —  On  the  under  surface  of  the  sternum 
and  cartilages  of  the  ribs  is  a  thin,  flat  muscle,  named  the  trian- 
giilaiis  sterni.  It  arises  from  the  ensiform  cartilage,  the  lower 
part  of  the  side  of  the  sternum,  and  the  cartilages  of  two  or 
three  lower  true  ribs.  Its  fibres  ascend  obliquely  outwards,  and 
are  inserted  by  fleshy  digitations  into  the  lower  borders  of  the 
cartilages  of  the  true  ribs  —  from  the  sixth  to  the  second.  Its 
lowest  digitation  runs  transversely  outwards  ;  each  successive 
one,  however,  becomes  more  oblique,  so  that  the  highest  one  is 
nearly  vertical  in  direction.  The  muscle  is  evidently  a  continu- 
ation upwards  of  the  anterior  portion  of  the  transversalis  abdom- 
inis. Its  actioji  is  to  draw  down  the  costal  cartilages,  and  thus 
it  acts  in  expiration.  Its  nerves  come  from  the  intercostal 
nerves,  its  arteiies  from  the  internal  mammary. 

Internal  Mammary  Artery.  —  This  artery  is  given  off  from 
the  subclavian  in  the  first  part  of  its  course  opposite  the  thyroid 
axis.     It  passes  down  behind  the  clavicle,  and  on  entering  the 


172  LYMPHATIC    GLANDS. 

chest  it  lies  between  the  cartilage  of  the  first  rib  and  the  pleura, 
and  is  crossed  by  the  phrenic  nerve.  It  then  descends  perpen- 
dicularly, about  half  an  inch  {12.^  mm.)  from  the  sternum,  lying 
on  the  pleura  and  behind  the  costal  cartilages ;  lower  down  it 
gets  between  the  cartilages  of  the  ribs  and  the  triangularis 
sterni,  as  far  as  the  seventh  costal  cartilage,  where  it  divides 
into  two  branches,  the  inusciilo-phrc7iic  and  the  superior  epigas- 
tric.^ The  latter  branch  then  enters  the  wall  of  the  abdomen 
behind  the  rectus  abdominis,  and  finally  inosculates  with  the 
deep  epigastric  (a  branch  of  the  external  iliac).  The  branches 
of  the  internal  mammary  are  as  follows  :  — 

a.  Artcria  contcs  incrvi  phrenici.  —  A  very  slender  artery,  which  accompanies 
the  phrenic  nerve  between  the  pleura  and  pericardium  to  the  diaphragm,  and 
anastomoses  with  the  phienic  branches  of  the  abdominal  aorta  and  internal  mam- 
mary. 

b.  Mediastinal,  pericardic,  sternal,  and  thymic.  —  These  branches  supply  the 
cellular  tissue  of  the  anterior  mediastinum,  the  pericardium,  and  the  triangularis 
sterni.  The  thymic  are  only  visible  in  childhood,  and  disappear  with  the  thymus 
gland. 

c.  Anterio}-  intercostal.  —  Two  for  each  intercostal  space  are  distributed  to  the 
five  or  six  upper  intercostal  spaces.  They  pass  outwards,  and  lie  at  first  between 
the  pleura  and  the  internal  intercostal  muscle,  and  subsequently  between  the  two 
intercostals.     They  inosculate  with  the  intercostal  arteries  from  the  aorta. 

d.  'Y\i%  perforating  arteries  pass  through  the  same  number  of  intercostal  spaces 
as  the  preceding  branches,  and  supply  the  pectoral  muscle  and  skin  of  the  chest. 
In  the  female  they  are  of  large  size  (especially  the  third),  to  supply  the  mammary 
gland. 

e.  The  musculo  phrenic  branch  runs  outwards  behind  the  cartilages  of  the  false 
ribs,  pierces  the  attachment  of  the  diaphgram,  and  tenninates  near  the  last  inter- 
costal space.  It  supplies  small  branches  to  the  diaphragm,  to  the  sixth,  seventh, 
and  sometimes  the  eighth  intercostal  spaces. 

Two  venae  comites  accompany  the  artery,  and  form  a  single 
trunk  at  the  upper  part  of  the  chest,  which  terminates  in  the 
brachio-cephalic  vein  of  its  own  side. 

Lymphatic  Glands. —There  are  several  lymphatic  glands 
in  the  neighborhocxl  of  the  internal  mammary  artery.  They 
receive  the  lymphatics  from  the  upper  part  of  the  abdominal 
wall,  the  diaphragm,  the  inner  portion  of  the  mammary  gland, 
and  the  intercostal  spaces.  On  the  right  side  they  terminate  in 
the  right  lymphatic  duct,  on  the  left  in  the  thoracic  duct. 
In  disease  of  the  inner  portion  of  the  mamma  these  glands  may 
enlarge  without  any  enlargement  of  tho.se  in  the  axilla. 

*  The  widest  intercostal  space  is  the  tliird.  Then  tlie  second,  and  finally  the 
first.  This  may  be  of  value  in  wounds  of  the  chest,  when  the  internal  mammary 
has  to  be  I'gated.     Ca'e  should  be  taken  not  lo  open  the  pleural  cavity.  —  A.  H. 


PLEURA. 


173 


Pleura.  —  As  the  lungs  are  constantly  gliding  to  and  fro 
within  the  chest  they  are  provided  with  a  serous  membrane  to 
facilitate  their  motion.  I'his  membrane  is  termed  the  pleura. 
There  is  one  for  each  lung.  Each  pleura  forms  a  completely 
closed  sac,  and,  like  all  other  serous  sacs,  has  a  farictal  and  a 
visceral  layer — that  is,  the  first  layer  lines  the  containing  walls, 
the  latter  is  reflected  over  the  contained  organ  or  viscus.  Its 
several  parts  are  named  after  the  surface  to  which  they  adhere  ; 
the  parietal  layer,  which  lines  the  ribs  and  intercostal  muscles, 
is  called  pleura  costalis ;  the  visceral  layer,  which  invests  the 
\\\x\g?>,  pleura  pulmonis;  between  these  two  layers  is  a  space 
which  is  termed  the  cavity  of  tJie pleura. 


Internal  mam- 
mary a. 


Phrenic  n. 


CEsophagus  with 
pneumogastric 


Cavity  of  the 
pleura. 


Fig.  62.  —  Diagram  OF  the  Reflections  of  the  Pleural  Sacs  in  Dotted  Lines. 

Each  pleura  occupies  its  own  half  of  the  thorax  ;  they  do  not 
communicate  with  one  another,  nor  do  they  come  into  contact 
with  each  other,  except  for  the  short  distance  of  about  two 
inches  (5  cm)  in  front,  behind  the  sternum. 

Unlike  the  peritoneum,  the  pleura  forms  no  folds  except  a  small 
one,  called  ligamentium  latum  pulmonis,  which  extends  from  the 
root  of  the  lung  to  the  diaphragm. 

The  pleura  costalis  (Fig.  62),  in  front,  lines  part  of  the  back 
of  the  sternum  and  the  inner  surfaces  of  the  costal  cartilages ; 
laterally,  it  is  reflected  over  the  ribs  and  the  intercostal  muscles  ; 
posteriorly,  it  is  traced  over  the  sides  of  the  bodies  of  the  tho- 
racic vertebrae ;  thence  it  passes  to  the  back  of  the  pericardium, 


174 


PLEURA. 


over  the  posterior  aspect  of  the  root  of  the  lung.  It  may  now 
be  traced,  as  \.\\q  pleura piilmonalis,  over  the  surface  of  the  lung, 
to  which  it  is  intimately  adherent,  into  the  fissures  between  the 
lobes,  as  far  as  the  anterior  border  of  the  lung  ;  thence  round  its 
pericardial  aspect  to  the  front  of  the  root  of  the  lung,  passing 
forwards  over  the  pericardium  to  the  back  of  the  sternum.  Its 
only  reflection,  the  ligamentum  latum  pulmonis,  has  been  already 
alluded  to.     Below,  the  pleura  covers  the  diaphragm. 

The  pleura  rises  as  a  conical  dome  into  the  base  of  the  neck, 
about  an  -inch  {2.5  cm.)  above  the  clavicle,  and  is  strengthened 
in  this  situation  by  expansions  from  the  scaleni  muscles.* 

The  thickness  of  the  pleura  differs  :  on  the  lung  it  is  thin, 
semi-transparent,  and  firmly  adherent  ;  on  the  ribs  and  diaphragm 
it  is  thick,  and  may  be  easily  separated  from  its  osseous  and 
muscular  connections.! 

The  spaces  called  anterior  2s\dL  posterior  mediastina,  formed 
by  the  separation  of  the  pleurae,  will  be  described  further  on. 

In  health  the  internal  surface  of  the  pleura  is  smooth,  polished, 
and  lubricated  by  moisture  sufficient  to  facilitate  the  sliding  of 
the  lung.  When  this  surface  is  thickened  and  roughened  by 
inflammation,  the  moving  lung  produces  a  friction  sound. 
When  the  pleural  sac  is  distended  by  serum,  it  constitutes 
hydrothorax ;  when  by  pus,  empyema ;  when  by  air,  pneumo- 
thorax ;  when  by  blood,  hsemo-thorax. 

Introduce  your  hand  into  the  pleural  sac,  and  ascertain  that 
the  reflection  of  the  pleural  on  to  the  diaphgram  corresponds 
with  an  imaginary  line  commencing  at  the  lower  part  of  the 
sternum  and  sloping  along  the  cartilages  of  the  successive  ribs 
down  to  the  lower  border  of  the  last  rib.  Supposing  a  ball  to 
lodge  in  the  pleural  sac,  it  might  fall  upon  the  dome  of  the  dia- 
phragm, and  roll  down  to  the  lowest  part  of  the  pleural  cavity. 
The  place,  therefore,  to  extract  it,  would  be  in  the  back,  at  the 
eleventh  intercostal  space.  The  operation  has  been  done  dur- 
ing life  with  success. 

If  a  transverse  section  were  made  through  the  chest  {see  Fig. 

*  A  .slip  is  described  by  Sibson  as  passing  from  the  transverse  process  of  the 
last  cervical  vertebra,  and,  .spreading  out,  is  inserted  into  the  pleural  dome  and  the 
inner  margin  of  the  first  rib. 

t  From  the  prevertebral  fascia,  a  ligamentous  band  passes  downwards  along 
the  inner  border  of  the  lung  to  be  attached  to  the  pericardium  and  the  central 
tendon  of  the  diaphragm.  As  it  passes  downwards  it  embraces  the  root  of  the 
lung,  and  supports  it  in  its  proper  position.  This  band  has  been  described  as  the 
"suspensory  ligament  of  the  diaphragm,"  by  Teuilel)en. 


MEUIASTINA. 


175 


62),  you  would  observe  that  as  the  pleurae  nowhere  come  into 
actual  contact,  a  space  is  left  between  them  extending  from  the 
sternum  to  the  spine,  and  which  is  larger  in  the  middle  than  in 
front  or  behind.  This  interval  is  called  by  anatomists  the  iti- 
terpleiiral  space  or  the  mediastinum,  and  for  convenience'  sake  is 
subdivided  into  three  parts  —  an  anterior,  middle,  ;xnd  posterior 
mediastiniifn. 

Mediastina,  Anterior,  Middle,  and  Posterior.  —  The  vu- 
diastina  are  the  space  which  the  two  pleural  sacs  leave  between 
them  in  the  antero-posterior  plane  of  the  chest,  and  which  con- 
tain all  the  thoracic  viscera  except  the  lungs.  There  is  an  an- 
terior, a  middle,  and  a  posterior  mediastinum.  To  put  these 
spaces  in  the  simplest  light,  let  us  imagine  the  heart  and  lungs 
to  be  removed  from  the  chest, 
and  the  two  pleural  sacs  to  be 
left  in  it  by  themselves.  The 
two  sacs,  if  inflated,  would  then 
appear  like  two  bladders,  in  con- 
tact only  in  the  middle,  as  shown 
by  the  dotted  outlines  in  the  an- 
nexed scheme  (Fig.  63).  The 
interval  marked  a,  behind  the 
sternum,  would  represent  the 
anterionnediastifinni ;  the  inter- 
val b,  the  posterior  mediastinum. 
Now  let  us  introduce  the  heart 
again,  between  the  two  pleural 
sacs  :  these  must  give  way  to  make  room  for  it,  so  that  the  two 
sacs  are  largely  separated  in  the  middle  line  of  the  chest  ;  and 
the  space  thus  occupied  by  the  heart  and  large  vessels  takes  the 
name  of  the  middle  mediastinum. 

Looking  at  the  chest  in  front,  the  anterior  mediastinum  ap- 
pears as  shown  in  the  diagram  (Fig.  64).  It  is  not  precisely 
vertical  in  its  direction,  for  it  inclines  slightly  towards  the  left, 
owing  to  the  position  of  the  heart.  Its  area  varies  ;  thus  it  is 
very  shallow  from  before  backwards  ;  it  is  extremely  narrow  in 
the  middle  where  the  edges  of  the  lungs  nearly  meet ;  it  is  wider 
above,  and  widest  of  all  below,  where  the  lungs  diverge.  Poste- 
riorly it  is  limited  by  the  pericardium  covering  the  heart,  aorta, 
and  its  branches,  and  the  pulmonary  artery. 

What  parts  are  contained  in  the  anterior  mediastinum  t  The 
remains  of  the  thymus  gland,  the  origins  of  the  sterno-hyoid. 


Fig.  63. 


\j6  MEDIASTINA, 

sterno-thyroid,  and  triangularis  sterni  muscles,  the  left  bracio- 
cephalic  vein  (which  crosses  behind  the  first  bone  of  the  ster- 
num), a  few  lymphatic  glands,  and  the  left  internal  mammary 
artery  and  vein. 

The  posto'ior  mcdiastinmn  (Fig.  62)  is  triangular  in  shape, 
placed  in  front  of  the  thoracic  vertebrae  ;  it  contains  the  oesopha- 
gus, the  two  pneumogastric  nerves,  the  descending  aorta,  the 
thoracic  duct,  the  greater  and  smaller  azygos  veins,  the  left 
superior  intercostal  vein,  and  some  lymphatic  glands.  This 
space  will  be  described  in  detail  at  a  later  stage. 

The  middle  mcdiastimiju  is  the  largest  of  the  mediastina,  and 
contains  the  heart  enclosed  in  the  pericardium,  the  vena  cava 
superior,  the  ascending  aorta,  the  pulmonary  arteries  and  veins, 
the  phrenic  nerves  with  their  accompanying  arteries,  and  the 
bifurcation  of  the  trachea. 

A  superior  mediastinum  has  also  been  described,  comprising 
that  part  of  the  interpleural  space  which  lies  above  a  horizontal 
plane,  extending  behind  from  the  lower  part  of  the  body  of  the 
fourth  thoracic  vertebra  to  the  articulation  between  the  manu- 
brium and  gladiolus  in  front.  The  contents  of  this  mediastinum 
include  all  those  structures  found  above  this  nearly  horizontal 
plane,  and  are  the  transverse  portion  of  the  arch  of  the  aorta 
and  its  three  large  branches,  the  trachea,  oesophagus,  and  tho- 
racic duct,  the  innominate  veins,  superior  vena  cava,  left  recur- 
rent laryngeal  nerve,  phrenic,  pneumogastric,  and  cardiac  nerves, 
lymphatic  glands,  and  the  thymus  or  its  remains. 

Before  passing  to  the  dissection  of  the  contents  of  the  thorax, 
the  student  should  carefully  trace  the  outline  of  the  free  borders 
of  the  pleurae  as  seen  in  the  front  of  the  chest.  As  the  mar- 
gins of  the  lungs  for  all  practical  purposes  correspond  with  the 
borders  of  the  pleurae,  we  shall  confine  our  description  to  the 
more  important  of  the  two  structures,  viz.,  the  lungs.  The  value 
of  this  investigation  is,  that  we  are  enabled  to  trace  upon  a  liv- 
ing chest  the  outlines  of  the  lungs,  and  know  what  parts  are 
naturally  resonant  on  percussion. 

Commencing  from  above  (Fig.  64),  we  find  that  the  apex  of 
the  lung  extends  into  the  neck,  from  an  inch  to  an  inch  and  a 
half  (2.5  to  J.y^  cm.)  above  the  clavicle.  This  part  of  the  lung 
ascends  behind  the  subclavian  artery  and  the  scalenus  anticus 
muscle,  and  deserves  especial  attention,  because  it  is,  more  than 
any  other,  the  seat  of  tubercular  disease.  From  the  sternal  end 
of  the    clavicles   the  lungs  converge  towards  the  middle  line, 


MEDIASTINA. 


177 


where  their  borders  nearly  meet  opposite  the  junction  of  the 
second  rib.  •  There  is  thus  little  or  no  lung  behind  the  manu- 
brium stern  i. 

From  the  level  of  the  second  costal  cartilage  to  the  level  of 
the  fourth,  the  inner  margins  of  each  lung  run  nearly  parallel 
and  almost  in  contact  behind  the  middle  of  the  sternum  ;  conse- 
quently they  overlap  the  great  vessels  at  the  root  of  the  heart. 

Below  the  level  of  the  fourth  costal  cartilage  the  margins  of 


Fig.  64.  —  Form  of  the  Lungs;  and  the  Extent  to  which  they  overlap  the  Heart  and 

ITS  Valves. 


the  lungs  diverge  from  each  other,  but  not  in  an  equal  degree. 
The  left  presents  the  notch  for  the  heart,  and  follows  nearly  the 
course  of  the  fourth  costal  cartilage  ;  at  the  lower  part  of  its 
curve  it  projects  more  or  less  over  the  apex  of  the  heart  like  a 
little  tongue.  The  rigJit  descends  almost  perpendicularly  behind 
the  sternum  as  low  as  the  attachment  of  the  ensiform  cartilage, 
and  then  turning  outwards  corresponds  with  the  direction  of  the 
sixth  costal  cartilage.      Hypertrophy  of  the  heart,  or  effusion 


178  RELATION    OF    LUNGS    TO    CHEST-WALL. 

into  the  pericardium,  will  not  only  raise  the  point  where  the 
lungs  diverge  above  the  ordinary  level,  but  also  increase  their 
divergence  ;  hence  the  greater  dulness  on  percussion.* 

Position  and  Form  of  the  Lungs.  —  The  two  lungs  are 
situated  in  the  chest  :  each  in  its  own  half  of  the  thorax,  with 
the  heart,  enclosed  in  its  pericardium,  between  them.  Each  fits 
accurately  into  the  cavity  which  contains  it.  Each,  therefore, 
is  conical  in  form;  the  apex  projects  into  the  root  of  the  neck, 
a  little  more  than  an  inch  (2.5  cm)  above  the  sternal  end  of  the 
clavical ;  the  base  is  broad  and  rests  on  the  diaphragm,  the  pos- 
terior part  being  thin  and  extending  as  far  as  the  eleventh  rib. 
Its  outer  SHjface  is  convex  and  adapted  to  the  ribs  ;  its  inner 
siuface  is  excavated,  to  make  room  for  the  heart  in  front  ;  and 
behind  presents  a  deep  fissure  —  Jiilnm  pnhnoiiis  —  for  the 
attachment  of  the  root  of  the  lung.  Vi's^ posterior  swxi?,<zQ,  is  con- 
vex, and  fits  into  the  concavity  of  the  thorax,  on  each  side  of 
the  spinal  column.  The  best  way  to  see  the  shape  of  the  lungs 
is  to  inject  them  through  the  trachea  with  wax,  which  is  tanta- 
mount to  taking  a  cast  of  each  thoracic  cavity.  In  such  a  prep- 
aration, besides  the  general  convexities  and  concavities  alluded 
to,  you  would  find  in  the  right  lung  a  little  indentation  for  the 
right  brachio- cephalic  vein  ;  in  the  left  an  indentation  for  the 
arch  of  the  aorta  and  the  left  subclavian  artery. 

Each  lung  is  divided  into  an  iipper  and  a  lower  lobe  by  a  deep 
fissure,  which  commences,  behind,  about  three  inches  {^ .^  cm) 
from  the  apex,  and  proceeds  obliquely  downwards  and  forwards 
to  the  junction  of  the  sixth  rib  with  its  cartilage  (Fig.  64). 
Speaking  broadly,  nearly  the  whole  of  the  anterior  portion  of  the 
lung  is  formed  by  the  upper  lobe  ;  nearly  the  whole  of  the  pos- 
terior portion  by  the  lower  lobe.  It  should  be  noticed,  however, 
that  the  upper  lobe  of  the  right  lung  is  divided  by  a  second  fis- 
sure which  marks  off,  from  its  lower  part,  a  triangular  portion 
called  its  middle  lobe. 

Relations  of  the  Lungs  to  the  Chest-Wall.  —  The  margins 
of  the  lungs  may  be  outlined  on  the  chest-wall  by  drawing  a  line 
through  the  sterno-clavicular  joint  to  the  middle  of  the  sternum, 
at  the  junction  of  the  manibrum  and  gladiolus.  These  margins 
continue  in  contact  behind  the  middle  of  the  sternum,  covered 
by  the  pleura  to  the  level  of  the  junction  of   the  fourth  costal 

*  Effusion  into  the  left  pleura  .sac  will  cause  the  tympanic  note  over  the  lunated 
portion  of  the  stomach  not  covered  by  the  liver  to  give  a  dull  or  flat  note  on  per- 
cussion.    TrauVje  s'milunar  area.  —  A.  H. 


POSITION    OF    THE    LUNGS    TO    CHEST-WALL. 


179 


cartilage  with  the  sternum.  The  margin  of  the  right  lung 
diverges  slightly  here  to  the  junction  of  the  sixth  cartilage  with 
the  sternum  ;  from  this  point  the  basal  margin  describes  a  curve 
which,  in  the  nipple  line,  touches  the  sixth  costo-chondral  articu- 
lation, in  the  mid-axillary  line  the  eighth  or  ninth  rib  according 


Fig.  65.  —  Anterior  View  of  the  Thorax  with  Outlines  of  the  Diaphragm  and 
Lungs.  (After  Morris.) 

to  the  age ;  lower  in  the  young  than  the  old,  and  terminates  at 
the  tenth  or  eleventh  thoracic  spine.  The  margin  of  the  left 
lung  diverges  from  the  mid-sternum,  at  fourth  costo-sternal  artic- 
ulation, horizontally  or  but  slight  obliquely  to  the  nipple,  then 
makes  a  tongue-like  projection  to  the  apex  of  the  heart  in  the 


I  So  PR.'ECORDIAL    REGION. 

fifth  interspace  and  crosses  the  sixth  costo-chondral  articulation  ; 
the  remaining  points  of  contact  being-  only  slightly  lower  than 
the  right  lung,  to  the  tenth  or  eleventh  thoracic  spine.  The 
space  between  the  lungs  in  mid-sternum,  it  must  be  remembered, 
is  larger  in  the  child,  owing  to  the  existence  of  the  thymus 
gland.  The  pleura  extends  lower  down  than  the  margins  of  the 
lungs  just  indicated,  in  the  child  as  low  as  the  twelfth  rib,  but 
in  the  adult  rarely  below  the  eleventh  in  the  axillary  line. 

In  penetrating  wounds  of  the  thorax  and  operations  for  the 
evacuation  of  inflammatory  products,  these  relations  should  be 
remembered  ;  but  as  the  sloping  of  the  diaphragm  leaves  such  a 
thin  space  between  the  costal  and  the  diaphragmatic  pleura, 
openings  in  the  axillary  line  should  never  be  made  below  the 
eighth  rib.      (A.  H.) 

The  dimensions  of  the  right  lung  are  greater  than  those  of 
the  left  in  all  directions  except  the  vertical ;  the  reason  of  this 
exception  is  the  greater  elevation  of  the  diaphragm  on  the  right 
side  by  the  liver.  On  an  average  the  right  lung  weighs  22 
ounces  {62^  grm  ),  the  left  20  ounces  {_^66  gnjt.). 

The  lungs  weigh  5V  of  the  total  weight  in  the  male,  4V  in  the 
female.  The  specific  gravity  is  0.7,  and,  according  to  some 
authors,  the  absolute  weight  in  the  male  is  1270  grammes 
(about  45  oz.) ;  in  the  female,  1030  grammes.  In  an  adult 
male  the  cubical  dimensions  of  the  lungs  are  7000  c.c,  i.e.,  dis- 
tended to  the  utmost.  The  dimensions  in  extreme  expiration, 
2500  c.c,  or  4500  c.c.  less  that  in  extreme  inspiration. 

The  constituents  of  the  root  of  the  lung  will  be  described  here- 
after when  they  can  be  more  satisfactorily  displayed. 

Prsecordial  Region.  —  The  prczcoj'dial  region  is  the  outline 
of  the  heart  traced  upon  the  front  wall  of  the  chest.  It  is  im- 
portant for  auscultatory  purposes  that  we  should  know  how  much 
of  the  heart  is  covered  and  separated  from  the  wall  of  the  chest 
by  intervening  lung  (F'ig.  64).  The  following  will  give  a  fair 
indication:  "Make  a  circle  of  two  inches  {^  cm.)  in  diameter 
round  a  point  midway  between  the  nipple  and  the  end  of  the 
sternum.  {Masto-XipJioid  /inc.)  This  circle  will  define,  suffici- 
ently for  all  practical  purposes,  that  part  of  the  heart  which  lies 
immediately  behind  the  wall  of  the  chest,  and  is  not  covered  by 
lung  or  pleura."  * 

This  part  of  the  praecordial  region  is  naturally  less  resonant 

*  Latham's  Clinical  Lectures. 


PR^>:CORDIAL    REGION. 


I«I 


to  percussion,  for  it  is  here  uncovered,  except  by  pericardium 
and  loose  connective  tissue,  nnd  lies  close  behind  the  thoracic 
wall.  In  the  rest  of  the  praecordial  region  the  heart  is  covered 
and  separated  from  the  chest  wall  by  intervening  lung. 

Where  should  we  put  the  stethoscope  when  we  listen  to  the 
valves  of  the  heart  ?     For  practical  purposes  it  is  enough  to 


Fig.  66.  —  Relative  Position  op  the  Heart  and  its  Valves  with  Regard  to  the 
Walls  of  the  Chest. 

The  valves  are  denoted  by  curved  lines.  The  aortic  tuilves  are  opposite  the  third  intercostal  space 
on  tlie  left  side,  close  to  the  sternum.  The  pu/mofiary  valves  are  just  above  the  aortic,  oppo- 
site the  junction  of  the  third  rib  with  the  sternum.  The  mitral  valves  are  opposite  the  third 
intercostal  space,  about  one  inch  to  the  left  of  the  sternum.  The  tricus/>iii  vah>es  lie  behind 
the  mic'dle  of  the  sternum,  abc  ut  the  level  of  the  fourth  rib  Aortic  7unr7)turs,  as  shown  by 
the  arrow,  are  propagated  up  tlie  aorta ;  mitral  tnurviiirs,  as  shown  by  the  arrow,  are  propa- 
gated towards  the  apex  of  the  heart. 


remember  that  the  mouth  of  an  ordinary  sized  stethoscope  will 
cover  a  portion  of  them  all,  if  it  be  placed  a  little  to  the  left  of 
the  mesial  line  of  the  sternum  opposite  the  third  intercostal 
space  (Fig.  64,  p.  177).  They  are  all  covered  by  a  thin  portion 
of  lung  ;  for  this  reason  we  ask  a  patient  to  stop  breathing  while 
we  listen  to  his  heart. 


102  PERICARDIUM. 

Position  and  Form  of  the  Heart.  The  heart  is  situated 
obliquely  in  the  chest  between  the  lungs.  Its  base,  i.e.,  the  part 
by  which  it  is  attached,  and  from  which  its  great  vessels  proceed, 
is  directed  upwards  towards  the  right  shoulder ;  its  apex  points 
downwards  and  to  the  left,  between  the  fifth  and  sixth  costal 
cartilages.  It  is  supported  towards  the  abdomen,  by  the  tendi- 
nous centre  of  the  diaphragm.  It  is  maintained  in  its  position 
by  a  membranous  bag  termed  the  pericardium,  which  is  lined  by 
a  serous  membrane  to  facilitate  its  movements.  The  pericardium 
must  first  claim  our  attention. 

Pericardium. —  T\\q  pericardium  is  the  conical  membranous 
bag  which  encloses  the  heart  and  the  large  vessels  at  its  base. 
It  is  broadest  below,  where  it  is  attached  to  the  tendinous  centre 
of  the  diaphragm,  and  to  the  muscular  part  in  connection  with 
the  tendon,  further  to  the  left  side  than  to  the  right ;  above,  it 
is  prolonged  over  the  great  vessels  of  the  heart,  about  two  or 
three  inches  ( 5  to  7.5  cm}j  from  their  origin,  and  is  connected 
with  the  depe  cervical  fascia.  O71  each  side,  it  is  in  contact  with 
the  pleura,* the  phrenic  nerve  running  down  between  them.  In 
front  of  it  is  the  anterior  mediastinum  ;  bcJiind\\.  is  the  posterior. 
Of  the  objects  in  the  posterior  mediastinum,  that  which  is  near- 
est to  the  pericardium  is  the  oesophagus  and  the  left  pneumo- 
gastric  nerve.  It  should  be  remembered  that  the  oesophagus  is 
in  close  contact  with  the  back  of  the  pericardium  and  left  auricle 
for  nearly  two  inches  (5  cvi^j  ;  this  fact  accounts  for  what  is 
sometime.?  observed  in  cases  of  pericarditis  where  there  is  much 
effusion ;   namely,  pain  and  difficulty  in  swallowing. 

The  pericardium  is  a  fibro-serons  membrane  and  consists  of 
two  layers — an  external  or  fibrous,  and  an  internal  or  serous. 
\\.s_ftbro?is  layer,  a  dense  membrane,  constitutes  its  chief  strength, 
and  is  attached,  below,  to  the  central  tendon  and  the  adjoining 
muscular  part  of  the  diaphragm.  Above,  it  forms  eight  tubular 
sheaths  for  the  great  vessels  at  the  base  of  the  heart  ;  namely, 
one  for  the  vena  cava  superior,  four  for  the  pulmonary  veins, 
two  for  the  pulmonary  arteries,  and  one  for  the  aorta.  The 
serous  layer  forms  a  shut  sac.  Its  parietal  layer  lines  the  fibrous 
layer  to  which  it  is  intimately  attached,  and  is  reflected  over  the 
great  vessels  and  the  heart  to  form  its  visceral  layer.  To  see 
where  the  serous  layer  is  reflected  over  the  vessels,  distend  the 

*  Some  muscular  fibres  have  been  pointed  out  by  Dr.  W.  S.  Forbes  in  the 
newly-born,  passing  from  the  muscular  fibres  of  the  diaphram  to  the  base  of  the 
fibrous  pericardium.  —  A.  H. 


PERICARDIUM.  I83 

pericardium  with  air.  Thus  you  will  find  that  this  layer  is 
reflected  over  the  aorta  as  high  as  the  commencement  of  the 
transverse  portion  of  the  arch  of  the  aorta.  It  is  reflected  over 
the  front  and  sides  of  the  vena  cava  superior. 

The  serous  layer  of  the  pericardium  covers  the  large  vessels 
to  an  extent  greater  than  is  generally  imagined  ;  though  the 
extent  is  not  precisely  similar  in  all  bodies.  The  aorta  and  pul- 
monary artery  are  enclosed  in  a  complete  sheath,  two  inches  (5 
cm.)  in  length,  so  that  these  vessels  are  covered  all  round  by  the 
serous  layer,  except  where  they  are  in  contact.  Indeed,  you  can 
pass  your  finger  behind  them  both,  through  a  foramen  bounded, 
in  front,  by  the  two  great  vessels  themselves ;  behind,  by  the 
upper  part  of  the  auricles  ;  and  above,  by  the  right  pulmonary 
artery.  Again,  the  back  of  the  aorta,  where  it  lies  on  the 
auricles,  is  covered  by  the  serous  pericardium.  The  superior 
cava  is  covered  all  round,  except  behind,  where  it  crosses  the 
right  pulmonary  artery.  The  inferior  cava  within  the  pericar- 
dium is  partly  covered  in  front.  The  left  pulmonary  veins  are 
covered  nearly  all  round  ;  the  right  less  so.  Behind  the  auricles, 
chiefly  the  left,  the  serous  layer  extends  upwards  in  the  form  of 
a  pouch,  rising  above  their  upper  border,  so  as  to  be  loosely 
connected  to  the  left  bronchus.  The  object  of  these  serous 
reflections  is  to  facilitate  the  free  action  of  the  heart  and  the 
great  vessels  at  its  base. 

In  the  healthy  state  the  capacity  of  the  pericardium  nearly 
corresponds  to  the  size  of  the  heart  when  distended  to  its  utmost. 
The  healthy  pericardium,  with  the  heart  in  situ,  may  be  made  to 
hold,  in  the  adult,  about  ten  ounces  of  fluid  {2g^.y  c.c).  The 
pericardium  is  not  extensile.  When  an  aneurism  bursts  into  it, 
death  is  caused,  not  by  loss  of  blood,  but  by  compression  of  the 
heart  in  consequence  of  the  inextensibility  of  the  pericardium. 

The  pericardium  derives  its  blood  from  the  internal  mammary, 
bronchial,  and  oesophageal  arteries  ;  its  nerve  supply  from  the 
phrenic  nerves. 

On  separating  the  left  pulmonary  artery  and  pulmonary  vein, 
you  will  notice  a  fold  of  serous  membrane  about  three-quarters 
of  an  inch  {18  mm.)  long,  and  about  one  inch  (2.^  cm.')  in  depth  ; 
this  is  the  vestigial  fold  of  the  pericardium  described  by  Mar- 
shall.*    It  passes  from  the  side  of  the  left  auricle,  curving  round 


*  "  On  the  Development  of  the  Great  Anterior  Veins  in  Man  and  Mammalia," 
Philosoph.  Transactions ;   1850. 


Fig.  67.— Ventral  Topography  ok  N'isckra  of  tiii-:  Thorax  and  Aiidomicn. 


»^*^. 


A. 


W 


Fig.  68.— Dorsal  Topouraphy  of  Viscera  of  the  Thorax  and  Abdomen. 


Fig.  69.— Right  Lati;ral  Topooraphy  ok  X'lsciiKA  oi-    riii-;  Thokax  and  Ahuo.vikn. 


Fig.  70. — Left  Lateral  Topography  of  Viscera  of  the  Thorax  and  Abdomen. 


i88 


POSITION    OF    THE    HEART. 


the  lower  left  pulmonary  vein,  to  the  left  superior  intercostal 
vein.  It  is  a  vestige  of  the  left  v.  c.  superior  (duct  of  Cuvier), 
which  exists  in  fcetal  life. 

Open  the  pericardium,  and  observe  that  the  heart  is  conical 
in  form,  and  convex  everywhere  except  upon  its  lower  surface, 
which  is  fiat,  and  rests  upon  the  tendinous  centre  of  the  dia- 
phrai^m.  When  the  pericardium  is  thus  laid  open,  the  following 
objects  are  exposed,  viz.  :     i.   Part  of  the  right  ventricle  ;  2.   Part 


Fig    71 


I     \1  IJU  M. 


Left  side  of  the  heart.  2.  Right  side  of  the  heart.  3.  Coronary  artery.  4.  Left  auricle. 
5.  Right  auricle.  6.  Superior  vena  cava.  7.  Pulmonary  artery.  8.  Origin  of  the  aorta. 
9.  Arch  of  the  aorta.  10,  Innominnte  artery,  11.  Right  common  caiotid  artery.  12. 
.Subclavian  arteries.  13.  Scalenus  amicus  muscle.  14.  I'irst  rib.  15.  I  arynx.  16.  Trachea. 
17.  Pneumogastric  nerve.  iS.  Phrenic  nerve.  19.  Right  lung.  20.  Left  lung.  21,  21. 
Diaphragm.     22,  22,   Seventh  rib. 


of  the  left  ventricle  ;  3.  Part  of  the  right  auricle  with  its  appen- 
dix overlapping  the  root  of  the  aorta;  4.  The  appendix  of  the 
left  auricle  ov^erlapping  the  root  of  the  pulmonary  artery ;  5. 
The  aorta;  6.  The  pulmonary  artery  ;  7.  The  vena  cava  supe- 
rior; 8.   The  right  and  left  coronary  arteries  (Fig.  71). 

Position  of  the  Heart.  —  Continued. — The  heart,  then, 
placed  behind  the  lower  half  of  the  sternum,  occupies  more  of 
the  left  than  the  right  half  of  the  chest,  and  rests  upon  the  ten- 


■      POSITION    OF    THE    HEART.  1 89 

dinous  centre  of  the  diaphragm,  which  is  a  Httle  below  the  lowest 
part  of  the  fifth  rib.  At  each  contraction  the  apex  of  the 
heart  may  be  felt  beating  between  the  cartilages  of  the  fifth' 
and  sixth  ribs,  about  two  inches  (5  cm.)  below  the  nipple  and  an 
inch  {2.^  cm.)  to  its  sternal  side,  or  about  three  and  a  half 
inches  {8.J  cm.)  to  the  left  of  the  middle  of  the  sternum.  Speak- 
ing broadly,  the  base  corresponds  with  a  line  drawn  across  the 
sternum  along  the  upper  borders  of  the  third  costal  cartilages. 
The  right  border  of  the  heart  is  formed  almost  entirely  by  the 
free  margin  of  the  right  auricle,  and,  when  distended,  bulges 
nearly  an  inch  {2.^  cm.)  to  the  right  of  the  sternum.  The  left 
border  of  the  heart  is  formed  by  the  round  border  of  the  left 
ventricle,  and  reaches  from  a  point,  commencing  at  the  second 
left  intercostal  space,  to  a  point  placed  two  inches  (5  cm.)  below 
the  nipple  and  an  inch  {2.^  cm.)  to  its  sternal  side.  The  hori- 
zontal border  is  formed  by  the  sharp  margin  of  the  right  ven- 
tricle, and  extends  from  the  sternal  attachment  of  the  fifth  right 
costal  cartilage  to  meet  the  lowest  point  of  the  left  margin. 
The  base  of  the  heart  corresponds  posteriorly  to  the  interval 
between  the  fifth  and  the  eighth  thoracic  vertebrae. 

The  normal  position  which  the  cardiac  valves  hold  to  the 
thoracic  walls  is  difficult  to  define  with  precision,  and  this  prob- 
ably accounts  for  the  discrepancies  noticed  in  anatomical  works 
on  this  subject.  The  following  relations  are  the  results  of  care- 
fully mide  observations  in  the  post-mortem  room  :  The  right 
auriculo-vcntncidar  valves  are  situated  behind  the  sternum  on 
the  level  of  the  fourth  costal  cartilage  ;  the  left  anriculo-ventri- 
ciilar  valves  are  opposite  the  third  intercostal  space,  about  one 
inch  {2.5  cm.)  to  the  left  of  the  sternum;  the  cusps  of  these 
valves  extend  as  low  as  the  fifth  costal  cartilage.  The  pulmo- 
nary valves  lie  immediately  behind  the  junction  of  the  third  left 
costal  cartilage  with  the  sternum  ;  the  aortic  valves  are  on  a  level 
with  the  upper  border  of  the  third  intercostal  space  just  at  the 
left  of  the  middle  line  of  the  sternum.* 

The  position  of  the  heart  varies  a  little  with  the  position  of 
the  body.  Of  this  any  one  may  convince  himself  by  leaning 
alternately  forwards  and  backwards,  by  lying  on  this  side  and  on 
that,  placing  at  the  same  time  his  hand  upon  the  praecordial 
region.      He  will  find  that  he  can,  in  a  slight  degree,  alter  the 

*  Anatomists  differ  much  in  the  description  they  ,ive  of  the  relations  of  the 
valves  to  the  thoracic  walls ;  in  fact  no  two  agree  in  all  the  details. 


190  BRACHIO-CEPHALIC    VEINS. 

place  and  the  extent  of  the  impulse  of  the  heart.  Inspiration 
and  expiration  also  alter  the  position  of  the  heart. 

The  student  should  now  make  out  the  large  vessels  in  connec- 
tion with  the  base  of  the  heart,  leaving  the  consideration  of  this 
organ  to  a  later  stage  of  the  dissection. 

Before  we  can  display  the  brachio-cephalic  veins,  the  layer  of 
the  deep  cervical  fascia  must  be  removed,  which  descends  over 
them  from  the  neck  and  is  lost  upon  the  pericardium.  Their 
coats  are  intimately  connected  with  this  fascia ;  and  one  of  its 
functions  appears  to  be  to  keep  the  veins  permanently  open  for 
the  free  return  of  blood  to  the  heart. 

Brachio-Cephalic  Veins.  —  The  light  and  left  brachio- 
cephalic (innominate)  veins  are  formed,  near  the  sternal  end  of 
the  clavicle,  by  the  confluence  of  the  internal  jugular  and  sub- 
clavian veins.  They  differ  in  their  course  and  relations,  and 
must,  therefore,  be  described  separately. 

The  left  brachio-cephalic  vein  passes  from  the  left  side 
obliquely  behind  the  first  bone  of  the  sternum,  the  sterno-hyoid 
and  thyroid  muscles,  the  remains  of  the  thymus  gland,  towards 
the  right  side,  to  form  with  the  right  innominate  vein  the  vena 
cava  superior  (Fig.  72,  p.  191).  It  is  about  three  inches  {y.^  cm.) 
in  length,  and  its  direction  inclines  a  little  downwards.  It  is 
larger  than  the  right  brachio-cephalic,  and  crosses  over  the 
trachea  and  the  origins  of  the  three  primary  branches  of  the  arch 
of  the  aorta.  We  are  reminded  of  this  fact  in  some  cases 
of  aneurism  of  these  vessels  —  for  what  happens.-'  The  vein 
becomes  compressed  between  the  aneurism  and  the  sternum  ; 
hence  the  swelling  and  venous  congestion  of  the  parts  from 
which  it  returns  its  blood  ;  namely,  of  the  left  arm,  and  the  left 
side  of  the  neck.  The  upper  border  of  the  vein  is  not  far  from 
the  upper  border  of  the  sternum  :  in  some  cases  it  lies  even 
higher,  and  we  have  seen  it  crossing  in  front  of  the  trachea  fully 
an  inch  {2.^  cm)  above  the  sternum.  This  occasional  deviation 
should  be  borne  in  mind  in  the  performance-  of  tracheotomy. 

The  right  brachio-cephalic  vein  descends  nearly  vertically  to 
join  the  superior  vena  cava,  opposite  the  first  right  intercostal 
space.  It  is  about  an  inch  and  a  half  (j./  cm.)  in  length,  and  is 
situated  about  one  inch  {2.^  cm.)  from  the  mesial  line  of  the  ster- 
num. On  its  left  side,  but  on  a  posterior  plane,  runs  the  arteria 
innominata  ;  on  its  right  side  is  the  pleura  (Fig.  'J2,  p.  191). 
Between  the  vein  and  the  pleura  is  the  phrenic  nerve.  The 
brachiocephali'c  veins  are  not  provided  with  valves.     The  veins 


VENA    CAVA    SUPERIOR. 


191 


which  generally  empty  themselves  into  the  right  and  left  brachio- 
cephalic are  as  follows  :  — 


The  Right  B.-C.  Vein  receives- 

The  vertebral 

The  internal  mammary. 

The  inferior  thyroid. 


The  Left  B.C.  Vein  receives- 

The  vertebral 

The  internal  mammary. 

The  inferior  thyroid. 

The  superior  intercostal. 

The  pericardiac. 

The  thymic. 


Opening  into  the  "point  of  junction  of  the  internal  jugular  and 
subclavian  veins,  on  the  right  side  is  the  right  lymphatic  duct ; 
on  the  left  side  is  the  thoracic  duct. 


Superior  intercostal. 

Internal  mammary. 

Vena  azygos. 


Middle  thyroid. 
Internal  jugular. 
External  jugular. 
Vertebral. 

Supra-scapular. 
Posterior  scapular. 

Subclavian. 


Internal  mammary. 

Pericardiac  and 
thymic. 

Left  superior  inter- 
costal. 


Fig.  72.— Superior  Vena  Cava  and  its  Tributaries. 

Vena  Cava  Superior.* —  This  is  the  great  vein  through 
which  the  impure  blood  from  the  head,  upper  extremities,  and 
chest  returns  into  the  right  auricle.  It  is  formed  by  the  junction 
of  the  right  and  left  brachio-cephalic  veins,  which  unite  at  nearly 
a  right  angle  opposite  the  upper  part  of  the  first  intercostal 
space  on  the  right  border  of  the  sternum  ;  that  is,  about  the  level 
of  the  highest  point  of  the  arch  of  the  aorta.  The  vena  cava 
descends  vertically,  with  a  slight  inclination  backwards,  to  the 
upper  and  anterior  part  of  the  right  auricle.  It  is  from  two  and 
a  half  to  three  inches  (6.2  to  '/.^  cm.)  long,  and  has  no  valves. 
The  lower  half  of  it  is  covered  by  the  pericardium  ;  you  must, 
therefore,  open  this  sac  to  see  how  the  serous  layer  of  the  peri- 
cardium is  reflected  over  the  front  and  sides  of  the  vein.     In 


*   Cephal  cava. 


192  ARCH    OF    THE    AORTA. 

respect  to  its  relations,  notice  that  the  vein  lies  in  front  of  the 
right  bronchus  and  the  right  pulmonary  vessels  ;  and  that  it 
is  overlapped  by  the  ascending  aorta,  which  lies  to  its  left  side. 
In  the  upper  half  of  its  course,  that  is,  above  the  pericardium,  it 
is  covered  on  its  right  side  by  the  pleura ;  on  this  side,  in  con- 
tact with  it,  descends  the  phrenic  nerve. 

Before  it  is  covered  by  the  pericardium,  the  vena  cava  receives 
the  right  veno  azygos,  which  opens  into  it  after  hooking  over 
the  right  bronchus  ;  also  some  pericardiac  and  mediastinal  veins. 

Course  of  the  Aorta.  — The  aorta  is  the  great  trunk  from 
which  all  the  arteries  of  the  body  carrying  arterial  blood  are  de- 
rived. It  commences  at  the  upper  and  back  part  of  the  left 
ventricle  of  the  heart.  It  ascends  forwards  and  to  the  right  as 
high  as  the  lower  border  of  the  first  intercostal  space  on  the 
right  side  ;  it  then  arches  backwards  towards  the  left  side  of 
the  body  of  the  second  thoracic  vertebra,  and  turning  down- 
wards over  the  left  side  of  the  third,"  completes  the  arch  at  the 
fifth  thoracic  vertebra.  The  aorta  descends  through  the  thorax 
on  the  left  side  of  the  bodies  of  the  remaining  thoracic  vertebrae 
as  far  as  the  diaphragm  ;  it  enters  the  abdomen  through  the 
aortic  opening  of  the  diaphragm,  and  descends  as  far  as  the  left 
side  of  the  body  of  the  fourth  lumbar  vertebra,  where  it  bifurcates 
into  the  right  and  left  common  iliac  arteries.  The  aorta  has 
received  different  names  in  the  various  parts  of  its  course  ;  thus, 
the  arched  portion  extending  from  its  origin  at  the  left  ventrical 
to  the  fifth  thoracic  vertebra,  is  called  the  arch  of  the  aorta  ;  the 
portion  between  this  vertebra  and  the  diaphragm  is  the  descend- 
mg  thoracic  aorta  ;  and  the  remainder  of  its  course  to  its  division 
at  the  fourth  lumbar  vertebra  is  known  as  the  abdoviinl  aorta. 

Course  and  Relations  of  the  Arch  of  the  Aorta.—  The 
arch  of  the  aorta,  as  before  stated,  commences  at  the  upper  part 
of  the  left  ventricle,  and  describes  an  arch  which  terminates  at 
the  fifth  thoracic  vertebra.  Its  origin  is  situated  behind  the  pul- 
monary artery,  and  on  the  left  side  of  the  middle  of  the  sternum, 
about  the  level  of  the  lower  border  of  the  third  costal  cartilage. 
The  direction  of  the  arch,  therefore,  is  from  the  sternum  to  the 
spine  and  rather  obliquely  from  right  to  left. 

For  convenience  of  description,  the  arch  of  the  aorta  is  divided 
into  an  ascending,  a  transverse,  and  a  descending  portion. 

Ascending  Portion. — To  see  this  portion  of  the  aorta,  the 
pericardium  must  be  opened.  You  then  observe  that  this  part 
of  the  artery  is  enclosed  all  round  by  the  serous  layer  of  the 


ARCH    OF    THE    AORTA. 


193 


pericardium,  except  where  it  is  in  contact  with  the  pulmonary 
artery.  It  is  about  two  inches  (5  cm.)  in  length,  and  ascends 
with  a  slight  curve,  the  convexity  looking  forwards  and  to  the 
right  side,  as  far  as  the  upper  border  of  the  second  costal 
cartilage  of  the  right  side,  where  it  lies  almost  in  contact  with 


3rd  cervical  n 

4th  cervical  n 

Pneumogas-    _ 
trie  n. 

5th  cervical  n.    - 


Cervicalis 
ascendens  a. 

Scalenus  amicus. 
Inferior  thyroid 
artery. 

Superficialis  colli 

a. 
Phrenic  n. 

Posterior 

scapular  a. 
Supra-scapular  a. 
Subclavian  a. 
Superior 

intercostal  a. 
Internal 

mamn^ary  a. 
Pneumogas  trie  n. 

Phrenic  n. 


Appendix  of  left 
auricle. 


Fig.  73. 

the  sternum.  Its  commencement  is  covered  by  the  pulmonary 
artery,  and  is  overlapped  by  the  appendix  of  the  right  auricle, 
and  higher  up  by  the  remains  of  the  thymus  gland.  On  its 
light  side,  but  on  a  posterior  plane,  is  the  superior  vena  cava 
and  the  right  auricle  ;  on  its  left  side  is  the  pulmonary  artery  ; 
behind  it  are  part  of  the  right  auricle,  the  right  pulmonary  artery 


194  ARCH    OF    THE    AORTA. 

and  \'cin,  and  the  root  of  the  right  king.  This  part  of  the  arch 
gives  off  the  right  and  left  coronary  arteries  for  the  supply  of 
the  heart. 

The  right  border  of  the  ascending  portion  of  the  arch  bulges 
to  the  right  of  the  sternum  to  the  extent  of  a  quarter  of  an  inch 
{6  mm.),  and  may  be  seen  at  the  sternal  end  of  the  second  right 
intercostal  space. 

The  arch  of  the  aorta  presents  partial  dilatations  in  certain  sit- 
uations. One  of  these,  called  the  great  simis  of  the  aorta,  is 
observed  on  the  right  side  of  the  arch,  about  the  junction  of  the 
ascending  with  the  transverse  portion  ;  it  is  little  marked  in  the 
infant,  but  increases  with  age.  Three  other  dilatations  (the 
sinuses  of  Valsalva),  one  corresponding  to  each  of  the  valves  at 
the  commencement  of  the  aorta,  will  be  examined  hereafter. 

Transverse  Portioti.  - —  This  portion  of  the  aorta  arches  from 
the  front  to  the  back  of  the  thorax,  and  extends  from  the  upper 
border  of  the  second  right  costal  cartilage  to  the  left  side  of  the 
third  thoracic  vertebra.  Its  highest  convex  portion  ascends 
usually  to  about  an  inch  {2.^  cm.)  below  the  upper  border  of  the 
sternum,  and  its  concavity  corresponds  with  the  articulation  of  the 
first  and  second  bones  of  the  sternum.  In  front  \\.  is  covered  by 
the  left  pleura  and  lung,  and  is  crossed  by  the  left  phrenic,  the 
left  pneumogastric,  the  superficial  cardiac  nerves,  the  pericardiac, 
and  the  left  superior  intercostal  veins.  Near  its  summit  nms 
the  left  brachio-cephalic  vein.  Within  its  concavity  are  the  left 
bronchus,  the  bifurcation  of  the  pulmonary  artery,  the  left  recur- 
rent laryngeal  nerve,  and  the  remains  of  the  ductus  arteriosus. 
The  artery  rests  upon  the  trachea  (a  little  above  its  bifurcation), 
the  deep  cardiac  plexus,  the  oesophagus,  the  thoracic  duct,  and 
the  left  recurrent  laryngeal  nerve.  From  the  upper  part  of  the 
transverse  portion  of  the  arch  arise  the  arteria  innominata,  the 
left  carotid,  and  the  left  subclavian  arteries  ;  and  lying  in  front 
of  these  arteries  is  the  left  brachio-cephalic  vein. 

Descending  Portion.  —  This  part  of  the  arch  lies  upon  the  left 
side  of  the  body  of  the  fourth  thoracic  vertebra,  and  at  the  lower 
border  of  the  body  of  the  fourth,  or  the  upper  part  of  the  fifth, 
thoracic  it  takes  the  name  of  the  descending  thoracic  aorta.  On 
its  rigJit  side  are  the  oesophagus  and  thoracic  duct  ;  on  its  left 
is  the  pleura  ;  in  front  are  the  pleura  and  the  root  of  the  left 
lung ;  behind,  it  lies  on  the  anterior  common  ligament,  corre- 
sponding to  the  fourth  thoracic  vertebra. 

What  parts  are  contained   within  the   arch  of  the  aorta  .?  - 


BRACHIO-CEPHALIC    OR    INNOMINATE    ARTERY.  I95 

The  left  bronchus,  the  right  pulmonary  artery,  the  left  recurrent 
nerve,  the  remains  of  the  ductus  arteriosus,  and  the  superficial 
cardiac  plexus  of  nerves. 

Relations  of  the  Arch  of  the  Aorta  to  the  Sternum. — 
These  relations  vary  according  to  the  size  of  the  heart,  the 
obliquity  of  the  ribs,  and  the  general  development  of  the  chest. 
In  a  well-formed  adult  the  ascending  aorta  is,  at  the  most  promi- 
nent part  of  its  bulge,  about  half  an  inch  {12.^  mm.)  behind  the 
first  bone  of  the  sternum.  The  highest  part  of  the  arch  is  about 
one  inch  {3.§  cm.)  below  the  upper  edge  of  the  sternum.* 

The  branches  given  off  from  the  ascending  portion  of  the  arch 
are  the  right  and  left  coronary  arteries,  which  pass,  one  in  front 
of,  and  the  other  behind,  the  heart  to  supply  its  muscular  tissue. 

The  right  coronary  artery  arises  from  the  anterior  sinus  of 
Valsalva,  and  passes  to  the  right  between  the  pulmonary  artery 
and  the  right  auricular  appendix,  running  in  the  auriculo-ven- 
tricular  groove. 

The  left  coronary  artery,  larger  than  the  preceding,  is  given 
off  from  the  left  posterior  sinus  of  Valsalva,  and  passes  between 
the  pulmonary  artery  and  left  auricular  appendix  ;  it  runs  down 
in  the  anterior  interventricular  sulcus  towards  the  apex  of  the 
heart. 

The  further  description  of  these  vessels  will  be  considered  in 
the  dissection  of  the  heart. 

From  the  highest  part  of  the  arch  arise  three  large  arteries 
for  the  head,  neck,  and  upper  limbs ;  namely,  the  brachio-cepha- 
lic  or  innominate  artery,  the  left  carotid,  and  the  left  subclavian. 

Brachio-cephalic  or  Innominate  Artery.  — This,  the  lar- 
gest of  the  three,  arises  from  the  commencement  of  the  transverse 
part  of  the  arch.  It  ascends  obliquely  towards  the  right,  and, 
after  a  course  of  about  one  inch  and  a  half  to  two  inches  {37.^ 
mm.  to  50  mm.),  divides  behind  the  right  sterno-clavicular  joint 
into  two  arteries  of  nearly  equal  size  — the  right  subclavian  and 
the  right  common  carotid. 


*  The  relations  of  the  arch  of  the  aorta  to  the  sternum  vary  even  in  adults, 
more  especially  if  there  be  any  hypertrophy  of  the  heart.  As  an  instance  among 
many,  we  may  mention  that  of  a  young  female  who  died  of  phthisis.  The  posi- 
tion of  the  aortic  valves  was  opposite  the  middle  of  the  sternum,  on  a  level  with 
the  middle  of  the  second  costal  articulation.  The  highest  part  of  the  arch  was  on 
a  level  with  the  upper  border  of  the  sternum  ;  the  arteria  innominata  was  situated 
entirely  in  front  of  the  trachea;  and  the  left  brachio-cephalic  vein  crossed  the 
trachea  so  much  above  the  sternum  that  it  would  have  been  directly  exposed  to 
injury  in  tracheotomy. 


196  LEFT    SUBCLAVIAN    ARTERY. 

The  relations  of  the  innominate  artery  are  as  follow  :  In  front 
it  has  the  manubrium  sterni,  the  right  sterno-clavicular  joint,  the 
origins  of  the  stemo-hyoid  and  thyroid  muscles,  the  remains  of 
the  thymus  gland,  the  left  brachio-cephalic  vein,  the  right  infe- 
rior thyroid  vein,  and  the  right  inferior  cervical  cardiac  branch 
of  the  pneumogastric  nerve.  BeJiind,  it  rests  upon  the  trachea. 
On  its  left  side  are  the  left  common  carotid  and  the  remains  of 
the  thymus.  On  its  right  side  are  the  lung  and  pleura,  the  right 
brachio-cephalic  vein,  and  the  pneumogastric  nerve. 

With  the  anatomy  of  the  parts  before  you,  you  can  understand 
that  an  aneurism  of  the  innominate  artery  might  be  distinguished 
from  an  aneurism  of  the  aorta —  i.  By  a  pulsation  in  the  neck 
between  the  sterno-mastoid  muscles,  i.e.,  in  the  fossa  above  the 
sternum;  2.  By  occasional  dyspnoea  owing  to  pressure  on  the 
trachea ;  3.  By  venous  congestion  in  the  left  arm  ;  4.  By  the 
aneurismal  thrill  being  confined  to  the  light  arm.* 

Left  Common  Carotid  Artery.  —  This  artery  arises  from 
the  arch  of  the  aorta,  close  to,  and  to  the  left  of,  the  arteria  in- 
nominata.  It  ascends  obliquely  to  the  left  sterno-clavicular 
joint,  and  thence  to  the  neck,  where  its  course  nearly  corre- 
sponds with  the  right  common  carotid  (p.  98).  In  front  it  has 
the  sternum,  the  left  stemo-hyoid  and  thyroid  muscles,  the  left 
brachio-cephalic  vein,  and  the  remains  of  the  thymus  gland  ; 
behind,  it  has  at  first  the  trachea,  and  higher  up  the  oesophagus 
and  thoracic  duct ;  to  the  right  side  is  the  innominate  artery  ;  to 
the  left  side  are  the  left  subclavian  artery  and  left  pneumogastric 
nerv^e. 

Left  Subclavian  Artery.  —  This  is  the  third  branch  of  the 
transverse  part  of  the  arch,  and  arises  from  it  opposite  the  third 
thoracic  vertebra.  It  ascends  nearly  vertically  out  of  the  chest 
to  the  inner  border  of  the  first  rib,  and  then  curves  outwards 
behind  the  scalenus  anticus.  Iti  fro7it  it  has  the  lung  covered 
with  pleura,  the  pneumogastric,  phrenic,  and  cardiac  nerves,  the 
left  common  carotid,  the  left  internal  jugular,  and  the  left  in- 
nominate veins,   the    sterno-hyoid,    sterno-thyroid,    and    sterno- 

*  If  the  innominate  artery  be  ligatured,  the  circulation  would  be  maintained 
by  the  following  collateral  branches  :  i.  Between  the  branches  of  the  two  external 
carotids,  which  anastomose  across  the  middle  line.  2.  Between  the  aortic  inter- 
co.stal  and  the  superior  intercostal.  3.  Between  the  aortic  intercostals  and  the 
internal  mammary,  long  thoracic,  alar  thoracic,  and  sub.scapular  arteries.  4.  I>e- 
tween  the  internal  mammary  and  deep  epigastric.  5.  Between  the  inferior  thyroid 
arteries.  6.  Between  the  two  vertebrals.  7.  Between  the  two  internal  carotid 
arteries. 


PHRENIC    NERVES    IN    THE    CHEST.  I97 

mastoid  muscles.  To  its  right  side  are  the  left  carotid,  oesopha- 
gus, and  trachea  ;  between  the  artery  and  the  oesophagus  is  the 
thoracic  duct  ;  to  its  left  side  is  the  lung  covered  with  pleura ; 
behind  it  are  the  longus  colli  muscle  covering  the  vertebrae,  the 
oesophagus,  thoracic  duct,  and  the  inferior  cervical  ganglion  of 
the  sympathetic.  The  upper  part  of  its  course,  where  the  vessel 
passes  in  front  of  the  apex  of  the  lung,  has  been  described  with 
the  anatomy  of  the  neck  (p.  130). 

Course  of  the  Phrenic  Nerves  through  the  Chest.  —  The 
phre?iie  nerve  comes  from  the  third,  fourth,  and  fifth  cervical 
nerves,  but  chiefly  from  the  fourth.  It  descends  on  the  scalenus 
anticus,  gradually  inclining  to  its  inner  border,  and  enters  the 
chest  between  the  subclavian  vein  and  artery.  It  then  crosses 
over  the  internal  mammary  artery  and  runs  in  front  of  the  root  of 
the  lung,  between  the  pleura  and  the  pericardium  to  the  diaphragm 
(Fig.  73,  p.  193),  to  the  under  surface  of  which  it  is  distributed. 

The  phrenic  nerve  is  joined  on  the  scalenus  anticus  by  an  off- 
set from  the  fifth  cervical  branch  of  the  brachial  plexus  ;  by 
another  filament  from  the  sympathetic  nerve ;  and  very  fre- 
quently by  a  small  loop  from  the  nerve  to  the  subclavius  muscle  ; 
occasionally  also  by  a  branch  from  the  descendens  hypoglossi. 

In  what  respects  do  the  phrenic  nerves  differ  from  each  other 
in  their  course.''  The  right  phrenic  runs  along  the  outer  side  of 
the  brachio-cephalic  yein  and  superior  vena  cava  ;  the  left  crosses 
in  front  of  the  transverse  part  of  the  arch  of  the  aorta  ;  besides 
which,  the  left  is  rather  longer  than  the  right,  since  it  curves 
over  the  apex  of  the  heart. 

Before  the  phrenic  nerve  divides  into  branches  to  supply  the 
diaphragm,  it  sends  off  minute  filaments  to  the  pleura  and  the 
pericardium ;  after  it  has  pierced  the  diaphragm  it  distributes 
branches  to  the  peritoneum.  The  right  phrenic  gives  off  one  or 
two  filaments,  which  unite  with  some  filaments  from  the  solar 
plexus  and  form  a  small  ganglion,  from  which  branches  are  dis- 
tributed to  the  supra-renal  capsule,  the  hepatic  plexus,  and  the 
inferior  vena  cava.  The  left  phrenic  gives  off  a  branch  which 
joins  a  twig  from  the  sympathetic  near  the  oesophageal  opening 
of  the  diaphragm,  but  there  is  no  appearance  of  a  ganglion. 

Having  studied  these  anatomical  details,  consider  for  a  moment  what  symp- 
toms are  likely  to  be  produced  by  an  aneurism  of  the  arch  of  the  aorta,  or  any  of 
the  primary  branches.  A  glance  at  the  important  parts  in  the  neighborhood  helps 
to  answer  the  question.  The  effects  will  vary  according  to  the  part  of  the  artery 
which  is  the  seat  of  the  aneurism,  and  accoiding  to  the  size,  the  form,  and  the 


198  DESCENDING    THORACIC    AORTA. 

position  of  the  tumor.  One  can  understand  that  compression  of  the  vena  cava 
superior,  or  either  of  the  brachio-cephahc  veins,  would  occasion  congestion  and 
cedema  of  the  parts  from  which  they  return  the  blood  ;  that  compression  of  the 
trachea  or  one  of  the  bronchi  might  occasion  dyspncea,  and  thus  simulate  disease 
of  the  larynx ;  *  that  compression  of  the  oesophagus  would  give  rise  to  symptoms 
of  obstruction.  Nor  must  we  forget  the  immediate  vicinity  of  the  thoracic  duct 
and  the  recurrent  nerve,!  and  the  effects  which  would  be  produced  by  their  com- 
pression. Can  one,  then,  be  surprised  that  a  disease  which  may  give  rise  to  so 
many  different  symptoms  should  be  a  fertile  source  of  fallacy  in  diagnosis  ? 

Thus  you  can  understand  how  aneurisms  of  the  aorta  may  prove  fatal  by  burst- 
ing into  the  contiguous  tubes  or  cavities ;  for  instance,  into  the  trachea,  the  oesoph- 
agus, the  pleura,  or  the  pericardium.  You  will  see,  too,  why  an  aneurism  of  the 
first  part  of  the  arch  is  so  much  more  dangerous  than  elsewhere.  The  reason  is, 
that  in  this  part  of  its  course  the  aorta  is  covered  only  by  a  thin  layer  of  serous 
membrane.  If  an  aneurism  takes  place  here,  the  coats  of  the  vessel  soon  become 
distended,  give  way,  and  allow  the  blood  to  tscape  into  the  pericardium — an  oc- 
currence which  is  speedily  fatal,  because,  the  pericardium  being  filled  with  blood, 
the  heart  is  prevented  from  acting. 

Posterior  Mediastinum  and  its  Contents. — The  pest erior 
mediastinum  (p.  176)  is  foimed  by  the  reflection  of  the  pleural 
sac  on  each  side,  from  the  root  of  the  lung  to  the  sides  of  the 
bodies  of  the  thoracic  vertebrae.  It  is  bounded  in  front  by  the 
pericardium  and  the  roots  of  the  lungs.  To  obtain  a  view  of  it, 
cut  away  the  ribs  nearly  as  far  as  their  angles,  draw  cut  the 
right  lung  towards  the  left  side,  and  fasten  it  firmly  to  the  left 
side  of  the  thorax.  Remove  the  pleura  of  the  right  side  frcm 
the  ribs,  and  the  posterior  aspect  of  the  root  of  the  right  lung, 
and  then  by  a  little  careful  dissection  the  space  and  the  struc- 
tures contained  in  it  will  be  displayed.  This  mediastinum  con- 
tains the  descending  thoracic  aorta  with  some  of  the  right  aortic 
intercostal  arteries  ;  in  front  of  the  aorta,  the  oesophagus,  with 
the  pneumogastric  nerves,  the  left  in  front  and  the  right  behind; 
on  the  right  of  the  aorta  is  the  vena  azygcs  major,  tttwccn  this 
vein  and  the  aorta  is  the  thoracic  duct  ;  superiorly  is  the  trachea; 
inferiorly  are  the  splanchnic  nerves  and  some  lymphatic  glands. 
To  expose  these  last  we  must  remove  the  pleura  and  a  layer  of 
dense  fascia  which  lines  the  chest  outside  it. 

Descending  Thoracic  Aorta.  —  We  have  already  traced  the 
arch  of  the  aorta  to  the  body  of  the  fifth  thoracic  vertebra 
(p.  194).  From  this  point  the  aorta  descends  on  the  left  side  of 
the  spine,  gradually  approaching  towards  the  middle  line.  The 
artery,  moreover,  following  the  thoracic  spinal  curve,  is  not  ver- 

*  In  the  Museum  of  Guy's  Hospital  there  is  a  preparation,  No.  1,487,  in  which 
laryngotomy  was  performed  under  the  circumstances  described  in  the  text. 

t  See  Med.  Gaz.,  Dec.  22,  1843  :  a  case  in  which  loss  of  voice  was  produced 
by  the  pressure  of  an  aneurismal  tumor  upon  the  left  recurrent  nerve. 


VENA    AZYGOS    MAJOR. 


199 


tical,  but  concave  forwards.  Opposite  the  last  thoracic  vertebra 
it  passes  between  the  crura  of  the  cliaphra<^m  and  enters  the  ab- 
domen. It  is  contained  in  the  posterior  mediastinum  ;  on  its 
left  side  it  is  covered  with  pleura  enclosing  the  left  lung,  and 
below  it  has  the  oesophagus  to 
the  left  ;  on  its  right  run  the 
vena  azygos,  the  oesophagus,  and 
thoracic  duct ;  in  front  of  it  are 
the  root  of  the  left  lung  and  the 
pericardium.  Lower  down  the 
oesophagus  is  in  front  of  the  ar- 
tery, and  subsequently  lies  a 
little  to  its  left  side ;  behind  are 
the  vertebral  column  and  the 
vena  azygos  minor.  Its  branches 
will  be  described  presently. 

Vena  Azygos  Major. — This 
vein  commences  in  the  abdomen 
opposite  the  first  or  second  lum- 
bar vertebra,  by  small  branches 
from  one  of  the  lumbar  veins  of 
the  right  side,  and  generally 
communicates  with  the  renal,  or 
the  vena  cava  itself.  This,  in- 
deed, is  the  main  point  about 
the  origin  of  the  vena  azygos, 
that  it  communicates  directly  or 
indirectly  with  the  vena  cava  in- 
ferior. It  enters  the  chest 
through  the  aortic  opening  of 
the  diaphragm,  and  ascends  on 
the  right  side  of  the  aorta 
through  the  posterior  mediasti- 
num, in  front  of  the  bodies  of 
the  lower  thoracic  vertebrae,  and 
over  the  right  intercostal  ar- 
teries. When  the  vein  reaches 
the  level  of  the  third  thoracic  vertebra  it  arches  forwards  over 
the  right  bronchus,  and  terminates  in  the  superior  vena  cava, 
just  before  this  vessel  is  covered  by  pericardium.  In  its  course 
it  receives  nine  or  ten  of  the  lower  intercostal  veins  of  the  right 
side,  the  spinal  veins,  the  posterior  mediastinal,  the  oesophageal, 


Fig.  74. —  Diagram  to  show  the  Course 
OF  THE  Vena  AzvGOS  and  the  Thoracic 
Duct. 


200  THORACIC    DUCT. 

and  the  right  bronchial  veins.  Opposite  the  sixth  or  seventh 
thoracic  vertebra  it  is  joined  by  the  left  vena  azygos.  It  is 
occasionally  connected  with  the  right  superior  intercostal  vein. 

The  left  vena  azygos,  vena  a:::ygos  mijior*  runs  up  the  left 
side  of  the  spine.  This  vein  commences  in  the  abdomen  frcm 
one  of  the  lumbar  veins  of  the  left  side,  or  from  the  left  renal. 
It  then  ascends  on  the  left  side  of  the  aorta  through  the  left  crus 
of  the  diaphragm.  On  a  level  with  the  sixth  or  seventh  thoracic 
vertebra  it  passes  beneath  the  aorta  and  thoracic  duct  to  join 
the  azygos  major.  Before  passing  beneath  the  aorta  it  usually 
communicates  with  the  left  superior  intercostal  vein.  It  gener- 
ally receives  six  or  seven  of  the  lower  intercostal  veins  of  the 
left  side,  the  oesophageal  and  mediastinal  veins.  These  azygos 
\'eins  are  provided  with  imperfect  valves,  and  are  supplemental 
to  the  inferior  vena  cava. 

The  left  upper  azygos  vein  f  receives  the  intercostal  vein  of 
the  left  side,  usually  from  the  fourth  to  the  sixth ;  it  communi- 
cates above  with  the  left  superior  intercostal  vein,  and  opens 
below,  either  directly  into  the  vena  azygos  major,  or  indirectly 
into  it  through  the  vena  azygos  minor. 

Thoracic  Duct  and  Receptaculum  Chyli.  —  The  tJioracic 
duct  (F"ig.  74)  is  a  canal,  from  fifteen  to  eighteen  inches  {37.5  to 
^5  cm.)  long,  through  which  the  contents  of  the  lacteal  vessels 
from  the  intestines  and  the  lymphatics  from  the  lower  limbs  are 
conveyed  into  the  blood.  These  vessels  converge  to  an  oval 
dilatation,  termed  rcceptacuhim  chyli  (cistern  of  Pecquet),  situ- 
ated a  little  to  the  right  side  of  the  front  of  the  body  of  the  sec- 
ond lumbar  vertebra,  behind  the  aorta  and  close  to  the  right  crus 
of  the  diaphragm.  Then,  getting  to  the  right  side  of  the  aorta, 
it  ascends  through  the  aortic  opening  of  the  diaphragm  into  the 
chest,  and  runs  up  the  posterior  mediastinum,  still  along  the 
right  side  of  the  aorta,  between  this  vessel  and  the  vena  azygos 
major,  and  opposite  the  sixth  thoracic  vertebra  crosses  over  the 
vena  azygos  minor.  Near  the  third  thoracic  vertebra  it  inclines 
to  the  left  side,  and  then  passes  behind  the  arch  of  the  aorta  and 
the  oesophagus,  and  ascends  on  the  left  side  of  this  tube,  be- 
tween it  and  the  left  pleura  ;  subsccjuently  the  duct  passes  up 
between  the  oesophagus  and  the  left  subclavian  artery,  as  high 
as  the  seventh  cervical  vertebra,  resting  on  the  longus  colli.      It 

*  This  may  be  called  Icnver  (caudal)  Icfl  azygos  and  vena  hemiazygos.  —  A.  H. 
t  This  may  l)e  called  vena  azygos  tertia,  or  vena  (cephal)  hemiazygos  accessoria. 
—  A.  II. 


CESOPHAGUS.  201 

then  emerges  from  beneath  the  carotid  sheath,  curves  down- 
wards over  the  subclavian  artery,  in  front  of  the  scalenus  anti- 
cus,  and  opens  into  the  back  part  of  the  confluence  of  the  left 
internal  jugular  and  subclavian  veins.  The  orifice  of  the  duct  is 
guarded  by  two  valves  which  permit  fluid  to  pass  from  the  duct 
into  the  vein,  but  not  vice  versa.  Valves,  disposed  like  those  in 
the  venous  system,  are  placed  at  short  intervals  along  the  duct, 
more  numerous  in  its  upper  part,  so  that  its  contents  can  only 
pass  upwards.*  The  diameter  of  the  duct  varies  in  different  parts 
of  its  course  ;  at  its  commencement  it  is  about  one-fourth  of  an 
inch  {6  mm.)  in  diameter,  at  the  sixth  thoracic  it  is  about  one- 
sixth  of  an  inch  {^  mm.),  and  it  enlarges  again  towards  the  ter- 
mination. It  receives  the  lymphatics  from  the  lower  extremities, 
and  from  all  the  abdominal  viscera  (except  the  convex  surface  of 
the  liver  and  the  abdominal  walls) ;  above  these  it  receives  the 
lymphatics  from  the  left  side  of  the  thorax,  the  left  lung,  the  left 
side  of  the  heart,  the  left  upper  extremity,  and  the  left  side  of 
the  head  and  neck. 

CEsophagus.  —  The  (rsophagus  is  that  part  of  the  alimentary 
canal  which  conveys  the  food  from  the  pharynx  to  the  stomach. 
It  commences  at  the  lower  border  of  the  fifth  cervical  vertebra, 
at  the  back  of  the  cricoid  cartilage  ;  runs  down  in  front  of  the 
spine,  to  the  right  side  of  the  transverse  portion  of  the  arch  of 
the  aorta,  then  through  the  posterior  mediastinum  in  front  of  the 
descending  aorta,  and  passes  through  the  oesophageal  opening  in 
the  diaphragm  to  end  in  the  stomach,  opposite  the  ninth  thoracic 
vertebra.  It  is  from  nine  to  ten  inches  [22.^  to  2^  cm.)  long. 
Its  course  is  not  exactly  straight,  for  it  describes  three  curv^es  — 
one  an  antero-posterior,  the  other  two  lateral  curves.  In  the 
neck  at  its  commencement  it  lies  at  first  in  the  middle  line  ;  it 
then  gets  behind,  and  a  little  to  the  left  of  the  trachea  ;  in  the 
chest,  i.e.,  about  the  fourth  thoracic  vertebra,  it  inclines  towards 
the  right  side  to  make  way  for  the  aorta  ;  but  it  again  inclines 
to  the  left  before  it  passes  through  the  diaphragm.  Its  antero- 
posterior curve  corresponds  to  the  curve  of  the  spinal  column. 

The  oesophagus,  in  the  neck,  rests  behind,  upon  the  front  of 


*  The  thoracic  duct  varies  in  size  in  different  individuals.  It  may  divide  in  its 
course  into  two  branches,  which  subsequently  reunite;  instead  of  one  there  may 
be  several  terminal  orifices.  Instances  have  been  observed  in  which  the  duct  has 
terminated  on  the  right  instead  of  the  left  side  (Fleischmann,  Leicheiioffnungen, 
1815;  also  Morrison,  Jotirttal  of  Anat.,  vol.  vi,  p.  427),  It  has  been  seen  to  ter- 
minate ill  the  vena  azygos  (Muller's  Archiv,  1834). 


202  CESOPHAGUS. 

the  spine  covered  by  the  longus  colli  muscle;  m.  front  it  has  the 
trachea  ;  on  each  side  it  is  in  relation  with  the  thyroid  body,  the 
common  carotid  (chiefly  the  left),  and  inferior  thyroid  arteries, 
and  the  recurrent  laryngeal  nerves  ;  to  the  left  of  it  is  the  thoracic 
duct. 

In  the  thorax,  the  oesophagus  has,  in  front,  the  trachea,  the 
left  bronchus,  the  arch  of  the  aorta,  the  left  carotid,  and  left 
subclavian  arteries  ;  and,  lastly,  for  about  two  inches  (5  cvi^,  the 
posterior  surface  of  the  pericardium  (behind  the  left  auricle)  ; 
this  accounts  for  the  pain  which  is  sometimes  experienced,  in 
cases  of  pericarditis,  during  the  passage  of  food  ;  behind,  it  rests 
upon  the  spinal  column,  the  longus  colli,  the  thoracic  duct,  the 
third,  fourth,  and  fifth  intercostal  arteries  of  the  right  side ;  and, 
lastly,  it  lies  in  front  of  and  slightly  to  the  left  side  of  the  aorta  ; 
hxtcrally,  the  aorta  and  pleura  are  to  the  left,  and  the  vena  azygos 
major  to  the  rigJit  of  the  tube.  As  it  passes  down  in  the  in- 
ter-pleural  space,  it  is  in  connection  with  both  pleurae.  The 
oesophagus  is  surrounded  by  a  plexus  of  nerves  formed  by  the 
pneumogastric  nerves,  the  left  being  in  front  of,  the  right 
behind  it. 

The  oesophagus  is  supplied  with  blood  by  the  inferior  thyroid, 
the  oesophageal  branches  of  the  aorta,  the  coronaria  ventriculi, 
and  the  left  phrenic  artery.  It  is  supplied  with  nerves  by  the 
pneumogastric  and  the  sympathetic,  which  ramify  betw^een  the 
two  muscular  layers.  The  oesophagus  is  composed  of  three 
coats,  an  external  or  muscular,  a  middle  or  areola,  and  an  internal 
or  mucous.  The  muscular  coat  consists  of  an  outer  longitudinal, 
and  an  inner  circular  layer  of  fibres.  The  longitudinal  layer  is 
particularly  strong,  and  arranged  in  the  upper  part  mainly  in 
three  fasciculi,  an  anterior  attached  to  the  vertical  ridge  on  the 
cricoid  cartilage,  and  two  lateral,  which  are  continuous  with  the 
inferior  constrictor;  these,  lower  down,  spread  out  and  form  a 
continuous  layer  round  the  oesophagus  and  support  the  circular 
fibres.  Under  the  microscope  the  muscular  fibres  composing 
the  upper  part  are  seen  to  consist  entirely  of  the  striped  variety; 
at  the  lower  part,  almost  exclusively  of  the  non-striped  variety. 
The  middle  coat  is  composed  of  areolar  tissue,  and  connects  very 
loosely  the  muscular  and  mucous  coats,  thereby  allowing  the 
mucous  membrane  to  move  very  freely  in  its  muscular  envelope. 
The  mucous  membrane  is  of  a  pale  color  and  considerable  thick- 
ness, and  in  the  contracted  state  of  the  oesophagus  is  arranged 
in  longitudinal  folds  within  the  tube,  which  lies  flattened  in  front 


PNEUMOGASTRIC    NERVKS.  2O3 

of  the  spine.  On  tlie  surface  of  the  mucous  membrane  there 
are  numerous  minute  papillrc  placed  obliquely.  It  is  lined  by  a 
very  thick  layer  of  scaly  epithelium.  In  the  submucous  tissue 
are  many  small  compound  racemose  glands  —  cesophageal  glands 
—  especially  towards  the  lower  end  of  the  oesophagus. 

Course  and  Branches  of  the  Pneumogastric  Nerves.  — 
The  course  of  the  pneumogastric  nerves  in  the  chest  is  not  the 
same  on  both  sides.  The  right  pneumogastric  nerve  enters  the 
chest  between  the  subclavian  artery  and  vein,  descends  behind 
the  right  innominate  vein  by  the  side  of  the  trachea  to  the  back 
of  the  root  of  the  lung,  where  it  breaks  up  into  a  plexus  forming 
the  posterior  pulmonary  plexus.  From  this  plexus  two  cords 
descend  to  the  posterior  surface  of  the  oesophagus,  upon  which 
they  divide  into  numerous  branches  ;  forming,  with  correspond- 
ing branches  of  the  left  pneumogastric  nerve,  the  oesophageal 
plexus  (plexus  giilce).  The  plexus  then  reunites  into  a  single 
trunk,  consisting  also  of  some  fibres  from  the  left  pneumogastric, 
and  passes  into  the  abdomen  through  the  oesophageal  opening  in 
the  diaphragm.  The  left  pneumogastric  descends  into  the  chest 
between  the  left  subclavian  and  carotid  arteries,  and  behind  the 
left  brachio-cephalic  vein.  It  then  crosses  in  front  of  the  arch 
of  the  aorta,  and  passes  behind  the  root  of  the  left  lung  to  the 
anterior  surface  of  the  oesophagus,  upon  which  it  also  assists  to 
form  a  plexus  with  the  nerve  of  the  right  side.  The  branches  of 
the  pneumogastric  nerve  in  the  chest  are  as  follow:  — 

a.  The  inferior  laryns^eal  or  recurrent.  —  This  nerve  on  the  right  side  turns 
under  the  subclavian  and  the  common  carotid  arteries  (Fig.  73,  p.  193) ;  on  the  left, 
under  the  arch  of  the  aorta,  below  the  ductus  arteriosus,  and  ascends  to  the  larynx. 
It  passes  beneath  the  inferior  thyroid  artery,  and  lying  in  the  groove  between  the 
trachea  and  oesophagus,  it  enters  the  larynx  beneath  the  lower  border  of  the  infe- 
rior constrictor  of  the  pharynx.  It  supplies  -with  motor  nei-ves  all  the  muscles 
which  act  upon  the  rima  glottidis,  except  the  cricothyroid  (supplied  by  the  exter- 
nal laryngeal  nerve).  As  they  turn  beneath  their  respective  arteries,  they  give  off 
branches  to  the  deep  cardiac  plexus ;  also  some  small  filaments  to  the  inferior  cer- 
vical ganglion  of  the  sympathetic.  In  the  neck  it  distributes  small  branches  to 
the  trachea,  oesophagus,  and  inferior  constrictor  muscle. 

h.  Cardiac  branches.  —  These  are  very  small,  and  join  the  cardiac  plexuses  (Fig. 
60,  p.  161);  the  right  arise  from  the  right  pneumogastric,  and  the  right  recurrent 
laryngeal,  close  to  the  trachea;  the  left  come  from  the  left  recurrent  laryngeal 
nerve.     On  both  sides  these  branches  pass  to  the  deep  cardiac  plexus. 

c.  Pulmonary  branches.  — These  accompany  the  bronchial  tubes.  The  greater 
number  run  behind  the  root  of  the  lung  and  constitute  the  posterior  pulmonary 
ple.xus.  A  few.  forming  the  anterior  pulmonary  plexus,  supply  the  front  part  of  the 
root  of  the  lung.  Both  these  plexuses  are  joined  by  filaments  from  the  second, 
third,  and  fourth  thoracic  ganglia  of  the  sympathetic.  The  nerves  of  the  lungs  are, 
however,  very  small,  and  cannot  be  traced  far  into  their  sukstance.* 

*  Upon  this  subject,  see  the  beautiful  plates  of  Scarpa. 


204  THORACIC    PORTION    OF    THE    SYMPATHETIC. 

d.  (Esophageal  plexus. —  Below  the  root  of  the  lung  each  pneumogastric  nerve 
is  subdivided  so  as  to  form  an  interlacement  of  nerves  round  the  cusophagus 
(plexus  gulic).  From  this  plexus  numerous  filaments  supply  the  coats  of  the 
lube ;  but  the  majority  of  them  are  collected  into  two  nerves  —  the  one,  chiefly 
the  continuation  of  the  left  pneumogastric  nerve,  lying  in  front  of  the  oesophagus; 
the  other,  chiefly  that  of  the  right,  lying  behind  it.  Both  nerves  pass  through  the 
oesophageal  opening  in  the  diaphragm  for  the  supply  of  the  stomach,  the  left  also 
sending  filaments  to  join  the  hepatic  plexus;  the  right  sending  branches  to  the 
cceliac,  splenic,  and  left  renal  plexuses. 

Having  examined  the  contents  of  the  posterior  mediastinum 
from  the  right  side,  now  do  so  from  the  left.  The  left  lung 
should  be  turned  out  of  its  cavity  and  fastened  by  hooks  towards 
the  right  side.  After  removing  the  pleura,  we  see  the  descend- 
ing thoracic  aorta,  the  pneumogastric  nerve  crossing  the  arch 
and  sending  the  recurrent  branch  under  it ;  also  the  first  part  of 
the  left  subclavian,  covered  externally  by  the  pleura.  The  pneu- 
mogastric nerv^e  must  be  traced  behind  the  root  of  the  left  lung 
to  the  oesophagus,  and  the  oesophageal  plexus  of  this  side  dis- 
sected. Lastly,  notice  the  lesser  vena  azygos,  which  crosses 
under  the  aorta  about  the  sixth  or  seventh  thoracic  vertebra  to 
join  the  vena  azygos  major. 

Thoracic  Portion  of  the  Sympathetic.  —  This  portion  of 
the  sympathetic  system  is  generally  composed  of  twelve  ganglia 
covered  by  the  pleura,  one  ganglion  being  found  over  the  head 
of  each  rib,  except  the  last  two,  which  lie  on  the  side  of  the 
bodies  of  the  vertebrae.  Often  there  are  only  ten  ganglia,  in 
consequence  of  two  of  them  being  fused  here  and  there.  The 
first  thoracic  ganglion  is  the  largest. 

The  ganglia  are  connected  together  by  thick  branches,  and 
each  ganglion  is  connected  externally  by  two  branches  with  the 
corresponding  intercostal  nerves.  The  nerves  proceeding  from 
the  ganglia  pass  inwards  to  supply  the  thoracic  and  part  of  the 
abdominal  viscera.  The  internal  branches  which  proceed  from 
the  six  upper  ganglia  are  small,  and  are  distributed  as  follows 
(Fig.  75,  p.  205):  — 

a.  Minute  nerv'cs  from  the  first  and  second  ganglia  to  the  deep 
cardiac  plexus. 

b.  Minute  nerves  from  the  third  and  fourth  ganglia  to  the 
posterior  pulmonary  plexus. 

The  branches  arising  from  the  six  lower  ganglia  unite  to  form 
three  nerves  — the  great  splancJinic,  the  lesser,  and  the  smallest 
splancJinic  netves. 

a.  Thegreal  splanchnic  nerve  is  generally  formed  by  branches  from  the  fifth  or 
sixth  to  the  tenth  ganglion,  and  also  receiving  filaments,  according  to  P.eck,  from 


INTERCOSTAL    MUSCLES. 


205 


all  the  thoracic  ganglia  above  the  sixth.  They  descend  obliquely  by  the  sides  of 
the  bodies  of  the  thoracic  vertebrne,  along  the  posterior  mediastinum,  and  unite 
into  a  single  nerve,  which  passes  through  the  corresponding  crus  of  the  diaphragm, 
and  joins  the  semilunar  ganglion  of  the  abdomen,  sending  also  branches  to  the 
renal  and  supra-renal  plexuses. 

b.  The  lesser  splaiic/inic  nei"ve  is  commonly  formed  by  branches  from  the  tenth 
and  eleventh  ganglia.  It  passes  through  the  crus  of  the  diaphragm  to  the  coeliac 
plexus,  and  occasionally  to  the  renal  plexus.* 

c.  The  smallest  splanchnic  nerve  comes 
from  the  twelfth  ganglion,  passes  through 
the  crus  of  the  diaphragm,  and  terminates  in 
the  lower  part  of  the  caliac  and  renal  plex- 
uses. (This  is  not  represented  in  the  dia- 
gram.) 

Intercostal     Muscles.  — -  The 

intercostal  muscles  fill  in  the  in- 
tervals between  the  ribs  and  are 
arranged  in  each  interval  in  two 
layers,  an  external  and  an  internal, 
which  cross  each  other  like  the 
letter  X.  The  external  intercostals, 
eleven  on  each  side,  run  obliquely 
from  behind  forwards,  like  the  ex- 
ternal oblique  muscle  of  the  abdo- 
men. They  connect  the  contiguous 
borders  of  the  ribs,  passing  from 
the  outer  lip  of  the  rib  above  to 
the  upper  border  of  the  rib  below  ; 
they  extend  from  the  tubercles  of 
the  ribs  behind  to  the  costal  carti- 
lages in  front,  and  are  continued 
forwards  to  the  sternum  as  a  thin 
membrane.  The  internal  run  from 
before  backwards  like  the  internal 
oblique,  and  pass  from  the  inner  lip 
of  the  groove  in  the  rib  above  and 
from  the  costal  cartilage,  and  are 
inserted  into  the  upper  border  of 
the  rib  below.  Observe  that  a  few  fibres  of  the  inner  layer  pass 
over  one  or  even  two  ribs,  chiefly  near  the  angles  (especially  of 
the  lower  ribs),  and  terminate  upon  a  rib  lower  down.f 

*  In  a  few  instances  we  have  traced  a  minute  filament  from  one  of  the  ganglia 
into  the  body  of  a  vertebra.  According  to  Cruveilhier  each  vertebra  receives 
one. 

t  These  irregular  muscular  bundles  are  called  the  subcostal  or  infracostal 
muscles. 


Fig.  75.  —  Diagram  of  the  Thoracic 
Portion  of  the  Sympathetic. 


206  INTERCOSTAL    ARTERIES. 

Neither  of  tnese  layers  of  intercostal  muscles  extends  all 
the  way  between  the  sternum  and  the  spine  ;  the  outer  layer, 
beginning  at  the  spine,  ceases  at  the  cartilages  of  the  ribs  ;  the 
inner  commencing  at  the  sternum,  ceases  at  the  angles  of  the 
ribs. 

The  intercostal  muscles  present  an  intermixture  of  tendinous 
and  fleshy  fibres  ;  and  they  are  covered  inside  and  outside  the 
chest  by  a  glistening  fascia,  to  give  greater  protection  to  the 
intercostal  spaces. 

The  external  intercostal  muscles  elevate  the  ribs,  and  are 
therefore  muscles  of  inspiration.  The  internal  intercostal  mus- 
cles depress  the  ribs,  and  are  therefore  muscles  of  expiration. 

Intercostal  Arteries. — There  are  ten  intercostal  arteries 
on  each  side  which  lie  between  the  internal  and  external  inter- 
costal muscles.  The  tzvo  upper  arteries  are  derived  from  the 
superior  intercostal  branch  of  the  subclavian ;  the  remaining 
eigJit  are  furnished  by  the  thoracic  aorta ;  and  since  this  vessel 
lies  rather  on  the  left  side  of  the  spine,  the  right  intercostal 
arteries  are  longer  than  the  left  ten.  The  tenth  runs  along  the 
lower  border  of  the  last  rib  and  should  be  called  the  subcostal 
artery.  The  upper  intercostal  arteries  from  the  aorta  ascend 
obliquely  to  reach  their  intercostal  spaces  ;  the  lower  run  more 
transversely.  They  are  given  off  from  the  back  of  the  descend- 
ing aorta,  and  as  they  pass  outwards  across  the  bodies  of  the 
vertebrae  they  are  covered  by  the  pleura  and  the  sympathetic 
nerves  ;  the  right,  in  addition,  pass  behind  the  oesophagus,  thor- 
acic duct,  and  the  vena  azygos  major ;  the  left  behind  the  left 
superior  intercostal  vein  and  the  vena  azygos  minor.  Having 
reached  the  intercostal  space,  each  artery  divides  into  an  anterior 
and  a  posterior  branch.  The  anterior  branch  in  direction  and 
size  appears  to  be  the  continuation  of  the  common  trunk.  At 
first  it  runs  along  the  middle  of  the  ijitercostal  space,  lying  upon 
the  external  intercostal  muscle,  and  separated  from  the  cavity  of 
the  chest  by  the  pleura  and  intercostal  fascia.  Here,  therefore, 
it  is  liable  to  be  injured  by  a  wound  in  the  back.  But  near  the 
angle  of  the  rib  it  passes  between  the  intercostal  muscles,  and 
occupies  the  groove  in  the  lower  border  of  the  rib  above.  Here 
it  gives  off  a  small  branch,  the  collateral  intercostal,  which  runs 
for  some  distance  along  the  upper  border  of  the  rib  below. 
After  supplying  the  muscles,  the  main  trunk  anastomoses  with 
the  anterior  intercostal  branch  of  the  internal  mammary  artery. 
In  some  cases  this  branch  is  as  large  as  the  intercostal  itself. 


THORACIC    NERVES.  207 

and  situated  so  as  to  be  directly  exposed  to  injury  in  the  opera- 
tion of  tapping  the  chest. 

In  its  course  along  the  intercostal  space,  each  artery  sends 
branches  to  the  intercostal  muscles  and  the  ribs.  About  midway 
between  the  sternum  and  the  spine,  each  gives  off  a  small 
branch,  which  accompanies  the  lateral  cutaneous  branch  of  the 
intercostal  nerve.  The  continued  trunk,  gradually  decreasing 
in  size,  becomes  very  small  towards  the  anterior  part  of  the 
space,  and  is  placed  more  in  the  middle  of  it.  Those  of  the  true 
intercostal  spaces  inosculate  with  branches  of  the  internal  mam- 
mary and  thoracic  branches  of  the  axillary  ;  those  of  the  false 
run  between  the  layers  of  the  abdominal  muscles,  and  anastomose 
with  the  epigastric  and  lumbar  arteries. 

The  posterior  or  dorsal  branch  passes  backwards  between  the 
transverse  processes  of  the  vertebrae,  on  the  inner  side  of  the 
anterior  costo-transv^erse  ligament,  and  is  distributed  to  the  mus- 
cles and  skin  of  the  back.  Each  sends  an  artery  through  the 
intervertebral  foramen  to  the  spinal  cord  and  its  membranes. 

On  the  right  side  the  intercostal  veins  terminate  in  the  vena 
azygos  major  ;  on  the  left,  the  seven  or  eight  lower  terminate  in 
the  vena  azygos  minor,  the  remainder  in  the  left  superior  inter- 
costal vein. 

The  usual  relation  which  the  intercostal  vessels  and  nerve 
bear  to  each  other  in  the  intercostal  space,  is,  that  the  vein  lies 
uppermost,  the  nerve  lozvest,  and  the  artery  between  them. 

Thoracic  Nerves.  —  The  thoracic  nerves  are  twelve  in  num- 
ber, the  first  emerging  between  the  first  and  second  thoracic 
vertebrae,  and  do  not  form  a  plexus  as  in  the  cervical,  lumbar, 
and  sacral  regions.  Each  thoracic  nerve  (like  all  the  spinal 
nerves)  arises  from  the  spinal  cord  by  two  roots,  an  anterior  or 
motor,  and  a  posterior  or  sensory.  The  sensory  root  has  a 
ganglion  upon  it.  The  two  roots  unite  in  the  intervertebral 
foramen  and  form  a  compound  nerve.  After  passing  through 
the  foramen,  it  is  connected  by  two  filaments  with  the  sympa- 
thetic nerve,  and  then  divides  into  an  anterior  and  a  posterior 
branch.  The  posterior  or  dorsal  branches  pass  backwards  be- 
tween the  transverse  processes  of  the  thoracic  vertebrae  and 
divide  into  internal  and  external  branches  ;  the  ijiternal  branches 
pass  between  the  multifidus  spinae  and  semispinalis  dorsi,  pierce 
the  rhomboidei  and  trapezius  muscles  ;  the  six  upper  branches 
become  cutaneous  at  the  spinus  processes  of  the  vertebrae  ;  the 
six  lower   supply  only  the  multifidus  spinae,  not  giving  off  any 


208 


INTERCOSTAL    NERVES. 


"^ 

POST^RboT' 

POST'S 

1  r^C^^^^ 

S^=^=^^f^ 

1 

Xant!  root 

ANT«B  / 

- 

LATV 
CUTS 

V 

ANT? CUT? 

Fig.  76.  —  Diagram  of  A  Spinal  Nervb. 


cutaneous   filaments  ;   the  external  branches   pass  through  the 
longissimus  dorsi  and  supply  this  muscle,   the   ilio-costalis  and 

their  continuations  and  the  leva- 
tores  costarum  ;  the  six  lower 
branches,  in  addition,  distribute 
cutaneous  filaments  to  the  skin. 
These  branches  will  be  described 
more  fully  later  on  in  the  dissec- 
tion of  the  back. 

Intercostal  Nerves. —  The  z'//- 
tercostal  nerves  are  the  anterior 
divisions  of  the  thoracic  nerves, 
and  are  twelve  in  number.  Each 
nerve  receives  a  filament  from  the 
sympathetic,  and  then  proceeds 
between  the  intercostal  muscles 
in  company  with,  and  immediately 
below,  the  corresponding  artery. 
Midway  between  the  spine  and  sternum,  they  give  off  lateral 
cutaneous  branches,  which  supply  the  skin  over  the  scapula  and 
the  thorax.  The  intercostal  nerves  terminate  in  front  in  the 
anterior  cutaneous  nei'ves.  In  the  anterior  part  of  the  intercostal 
space  the  nei-ves  lie  in  the  substance  of  the  internal  intercostal 
muscles,  and  at  the  costal  cartilages  get  to  the  inner  side  of  the 
muscles,  passing  between  them  and  the  pleura. 

The  intercostal  nerves  are  divided  into  two  sets  :  the  six  upper 
are  called  the  pectoral  intercostals,  because  they  supply  the  struc- 
tures of  the  pectoral  region;  the  six  lower,  the  abdominal  inter- 
costals, because  they  supply  the  chest  and  abdominal  walls. 

The  upper  or  pectoral  intercostal  nerves  pass  between  the  ex- 
ternal and  internal  intercostal  muscles,  run  forwards  in  the  sub- 
stance of  the  latter  muscle,  and  at  the  sternal  end  of  the  inter- 
costal spaces  pierce  the  internal  intercostal  muscles  and  the 
pectoralis  major,  to  be  ultimately  distributed  to  the  skin  of  the 
chest.  The  upper  intercostal  nerves  supply  the  levatores  cos- 
tarum, serratus  posticus  superior,  the  intercostals,  and  the  tri- 
angularis sterni. 

The  loiver  or  abdominal  intercostal  nerves  pass  like  the  upper 
nerves  between  the  intercostal  muscles  as  far  forwards  as  the 
costal  cartilages.  They  pass  behind  these,  and  then  run  between 
the  transversalis  and  internal  oblique,  as  far  as  the  outer  border 
of  the  rectus.     Piercing  the  sheath  of  the  muscle,  they  supply 


PULMONARY    ARTERY.  2O9 

it,  and  subsequently  end  as  the  anterior  cutaneous  nerves  of  the 
abdomen.  They  supply  the  intercostal  muscles,  the  serratus  pos- 
ticus inferior,  and  the  abdominal  parietal  muscles. 

Notice  that  the  first  thoracic  nerve  ascends  nearly  perpendicu- 
larly over  the  neck  of  the  first  rib  to  form  part  of  the  brachial 
plexus.  This  nerve,  however,  gives  off  a  small  branch,  the  first 
intercostal  nerve,  to  supply  the  first  intercostal  space.  This,  as 
a  rule,  has  no  lateral  cutaneous  branch. 

Intercostal  lympJiatic  glands.  —  These  are  situated  near  the 
heads  of  the  ribs  ;  there  are  some  between  the  layers  of  the  in- 
tercostal muscles.  They  are  of  small  size,  and  their  efferent 
vessels  go  into  the  thoracic  duct.  Some  of  the  upper  ones  on 
the  right  side  pass  into  the  right  lymphatic  duct.  We  have 
seen  these  intercostal  glands  enlarged  and  diseased  in  phthisis. 

Bronchial  and  CEsophageal  Arteries.  —  Small  bronchial 
arteries,  arising  on  the  right  side  most  frequently  from  the  first 
aortic  intercostal  (third  intercostal)  artery,  and  on  the  left  from 
the  thoracic  aorta,  accompany  the  bronchial  tube  on  its  posterior 
aspect  into  the  substance  of  the  lung.*  Their  distribution  and 
office  will  be  considered  with  the  anatomy  of  the  lung.  CEsopha- 
geal arteries,  four  or  five  in  number,  proceed  from  the  front  of 
the  thoracic  aorta  to  ramify  on  the  oesophagus,  where  they  inos- 
culate above  with  the  oesophageal  branches  of  the  inferior  thy- 
roid, and  below  with  the  oesophageal  branches  of  the  coionaria 
ventriculi  and  phrenic  arteries.  Small  posterior  mediastinal 
arteries  are  given  off  from  the  posterior  part  of  the  aorta,  and 
supply  the  lymphatic  glands  and  tissues  of  the  posterior  medias- 
tinum. 

Having  finished  the  posterior  mediastinum,  replace  the  lung, 
and  turn  your  attention  once  more  to  the  great  vessels  at  the 
root  of  the  heart. 

Pulmonary  Artery.  — This  vessel  is  about  two  inches  (5  r;;z.) 
in  length,  and  conveys  the  venous  blood  from  the  heart  to  the 
lungs.  It  proceeds  from  the  upper  part  of  the  base  of  the  right 
ventricle,  and  passes  upwards  and  backwards  along  the  left  side 
of  the  aorta  to  the  concavity  of  the  arch  of  the  aorta,  where  it 
divides  into  two  branches,  a  right  and  a  left,  one  for  each  lung. 
At  its  origin  it  has  on  each  side  an  auricular  appendix  and  a  cor- 
onary artery,  and  lies  in  front  of  the  root  of  the  aorta.     The 

*  On  the  left  side  there  are  usually  two  bronchial  arteries  —  a  superior,  arising 
from  the  highest  part  of  the  thoracic  aorta,  and  an  inferior,  arising  about  an  inch 
(  s.^  cm.)  lower  down. 


2IO  CARDIAC    NERVES. 

pulmonary  artery  and  the  aorta  are  surrounded  for  two  inches 
(5  ci>i.)  by  a  common  sheath  of  pericardium.  The  right  branch, 
the  larger  and  longer,  passes  horizontally  below  the  arch  of  the 
aorta,  behind  the  ascending  aorta  and  the  superior  vena  cava, 
to  the  root  of  its  lung ;  the  left  is  easily  followed  to  its  lung  by 
removing  the  layer  of  pericardium  investing  it,  when  it  will  be 
found  to  pass  horizontally  in  front  of  the  descending  aorta  and 
the  left  bronchus  to  the  root  of  the  left  lung. 

Search  should  be  made  for  a  short  fibrous  cord  which  con- 
nects the  commencement  of  the  left  pulmonary  artery  with  the 
concavity  of  the  arch  of  the  aorta.  This  cord  is  the  remains  of 
the  ductus  arteriosus,  a  canal  which  in  foetal  life  conveyed  blood 
from  the  pulmonary  artery  to  the  aorta. 

Draw  towards  the  left  side  the  first  part  of  the  arch  of  the 
aorta,  and  dissect  the  pericardium  from  the  great  vessels  at  the 
base  of  the  heart.  Thus  a  good  view  will  be  obtained  of 
the  trachea  and  its  bifurcation  into  the  two  bronchi.  Below  the 
division  of  the  trachea  the  right  pulmonary  artery  is  seen  passing 
in  front  of  the  right  bronchus.  The  superior  vena  cava  and 
aorta  are  seen  in  front  of,  and  nearly  at  right  angles  to,  the 
right  pulmonary  artery.  The  vena  azygos  major  is  seen  arching 
over  the  right  bronchus  and  terminating  in  the  vena  cava  supe- 
rior, just  before  this  vein  pierces  the  pericardium.  Notice, 
especially,  a  number  of  lymphatic  glands  called  broncJiial,  at  the 
angle  of  bifurcation  of  the  trachea.  The  situation  of  these 
glands  in  the  midst  of  so  many  tubes  explains  the  variety  of 
symptoms  which  may  be  produced  by  their  enlargement. 

Nerves  of  the  Heart  and  Cardiac  Plexuses.  —  The 
nerv'es  of  the  heart  come  from  the  pneumogastric  and  its  recur- 
rent branch,  and  the  three  cer\dcal  ganglia  of  the  sympathetic. 
The  pneumogastric  gives  off  (generally)  two  or  more  filaments 
(cardiac),  which  proceed  from  the  main  trunk  in  the  neck,  or 
from  its  recurrent  branch.  The  sympathetic  sends  three  (car- 
diac) filaments:  one  from  the  upper  cei-vical  ganglion,  a  second 
from  the  middle,  and  a  third  from  the  lower ;  and  they  are  called, 
respectively,  the  upper,  middle,  and  lower  cardiac  nerves  of  the 
sympathetic. 

The  minute  and  delicate  nerves  from  these  several  sources  on  each  side  pass 
downwards  to  the  base  of  the  heart.  They  vary  very  much  in  their  precise  rela- 
tions to  the  great  vessels  upon  which  they  run;  but,  speaking  generally,  it  may  be 
said  that  the  nerves  on  the  right  side  run  chiefly  behind  the  arch  of  the  aorta; 
those  on  the  left,  in  front  of  it.     Eventually  they  form,  by  their  mutual  subdivisions 


DEEP    CERVICAL    LYMPHATIC    GLANDS. 


21  I 


and  interlacement,  an  intricate  network  of  nerves,  termed,  according  to  their  posi- 
tion, the  superficial  and  the  deep  cardiac  plexus. 

The  superficial  and  smaller  cardiac  plexus  lies  in  the  concavity  of  the  arch  of 
the  aorta  in  front  of  the  right  pulmonary  artery.  It  is  closely  connected  with  the 
deep  plexus.  It  receives  the  upper  cardiac  branch  of  the  left  sympathetic,  the 
lower  cervical  cardiac  branch  from  the  left  pneumogastric,  and  filaments  from  the 
deep  plexus.  In  it  is  usually  found  a  small  ganglion,  ,^rtWi,'//(W  of  IVrisberg,  placed 
beneath  the  arch  of  the  aorta,  on  the  right  .side  of  the  ductus  arteriosus.  This 
plexus  distributes  branches  to  the  anterior  coronary  and  the  anterior  pulmonary 
plexuses. 


Fit;.  77.  —  Diagram  showing  the  Constituents  of  the  Root  of  Each  Lung,  and  their 
Relative  Position;  also  the  Position  of  the  Valves  of  the  Heart.  The  Arrows 
Indicate  the  Directions  in  which  Aortic  and  Mitral  Murmurs  ark  Propagated. 


The  deeper  and  lars^er  cardiac  plexus  is  situated  behind  the  arch  of  the  aorta  in 
front  of  the  bifurcation  of  the  trachea  and  immediately  above  the  right  pulmonary 
artery.  To  see  it  the  pericardial  covering  of  the  aorta  must  be  carefully  removed 
and  the  vessel  hooked  forwards  and  to  the  left.  This  plexus  is  formed  by  all  the 
cardiac  branches  of  the  right  and  left  sympathetic  ganglia,  and  by  the  cardiac 
branches  of  the  pneumogastric  and  recurrent  laryngeal  nerves,  e.xcept  the  left 
superior  cardiac  branch  of  the  sympathetic  and  the  left  cervical  cardiac  branch  of 
the  pneumogastric,  both  of  which  pass  to  the  superficial  cardiac  plexus.  The 
branches  from  the  rii^ht  side  of  this  plexus  descend  chiefly  in  front  of  the  pul- 
monary artery  and  pass  to  the  anterior  pulmonary  plexus  and  to  the  anterior  cor- 
onary plexus ;  a  few  branches  which  pass  behind  the  pulmonary  artery  are  dis- 


212  DISSECTION    OF    THE    HEART. 

tributed  to  the  right  auricle  and  to  the  posterior  coronary  plexus.  The  branches 
from  the  left  side  of  the  plexus  go  to  the  left  auricle,  the  anterior  pulmonary  plexus, 
but  chiefly  to  the  posterior  coronary  plexus. 

From  the  cardiac  plexuses,  as  a  common  centre,  the  nerves  pass  off  to  the 
heart,  forming  plexuses  around  the  coronary  arteries.  Thus,  the  anterior  corotiary 
plexus  (derived  chiefly  from  the  superficial  cardiac)  accompanies  the  anterior  cor- 
onary artery.  The  posterior  coronary  plexus  (derived  chiefly  from  the  left  side  of 
the  deep  cardiac)  runs  with  the  posterior  coronary  artery.  The  two  plexuses  com- 
municate at  the  apex  of  the  heart,  and  in  the  ventricular  septum. 

It  is  not  an  easy  matter  to  trace  the  nerves  into  the  substance 
of  the  heart.  For  this  purpose  a  horse's  heart  is  the  best,  and 
previous  maceration  in  water  is  desirable.  The  nerves  in  the 
substance  of  the  heart  are  pecuhar  in  this  respect ;  that  they  pre- 
sent minute  gangha  in  their  course,  which  are  presumed  to 
preside  over  the  rhythmical  contractions  of  the  heart. 

Constituents  of  the  Root  of  Each  Lung.  —  Draw  aside 
the  margin  of  the  right  lung ;  divide  the  superior  vena  cava 
above  the  vena  azygos,  and  turn  down  the  lower  part.  Remove 
the  layer  of  pericardium  which  covers  the  pulmonary  veins,  and 
the  constituent  parts  of  the  root  of  the  right  lung  will  be  exposed. 
It  is  composed  of  the  pulmonary  artery,  the  pulmonary  veins, 
bronchus,  bronchial  vessels,  anterior  and  posterior  pulmonary 
plexuses,  and  some  lymphatics.  The  following  is  the  disposition 
of  the  large  vessels  forming  the  root  of  the  lung.  In  front  are 
the  two  pulmonary  veins;  behind  the  veins  are  the  subdivisions 
of  the  pulmonary  artery ;  behind  the  artery  are  the  divisions  of 
the  bronchus.  From  above  downwards  they  are  disposed  thus : 
On  the  right  side  we  find  —  i  st,  the  bronchus ;  2d,  the  artery ; 
3d,  the  veins.  On  the  left  we  find — ist,  the  artery;  2d,  the 
bronchus;  3d,  the  veins  —  as  shown  in  Fig.  ']']. 

DISSECTION   OF  THE   HEART. 

Position. — The  heart  is  conical  in  form,  and  more  or  less 
convex  on  its  external  aspect,  with  the  exception  of  that  portion 
lying  on  the  tendinous  centre  of  the  diaphragm,  which  is  flat- 
tened. It  is  situated  obliquely  in  the  thorax  between  the  two 
lungs,  and  is  completely  surrounded  by  the  pericardium.  It  ex- 
tends from  the  fifth  to  the  eighth  thoracic  vertebra,  with  its  base 
directed  upwards,  backwards,  and  to  the  right,  its  apex  down- 
wards, forwards,  and  to  the  left,  where  during  life  it  beats  in  the 
fifth  intercostal  space,  two  inches  (5  cni^  below  the  nipple  and 
an  inch  {2.^  cm )  to  its  sternal  side.  The  position  which  the 
heart  bears  to  the  thoracic  walls  has  been  already  described  (p. 


THE    HEART.  213 

1 88);  it  varies,  however,  in  different  subjects,  and  as  a  rule  is 
hi<,d-ier  in  the  dead  body  than  in  the  hving,  owing  to  the  shrink- 
ing of  the  kings. 

The  anterior  surface  of  the  heart  is  convex  and  looks  upwards 
and  forwards;  the  posterior  surface  is  flattened  and  rests  upon 
the  diaphragm :  the  former  is  chiefly  formed  by  the  right  ven- 
tricle, the  latter  by  the  left  ventricle.  The  right  border  is  sharp 
{margo  acutiis)  ;  while  the  left  border  is  thick  and  rounded 
{inargo  obtusus). 

Size  and  Weight.  —  The  size  of  the  heart  is  dependent  upon 
so  many  conditions,  that  the  following  measurements  must  be 
received  with  more  or  less  limitation.  An  average  heart  will 
measure,  in  its  transverse  direction  at  the  base,  three  and  a  half 
inches  {S.'J  cm) ;  in  its  length,  about  five  inches  {12.^  cm) ;  in  its 
thickness,  two  and  a  half  inches  (6.2  cm).  The  weight  is  from 
ten  to  twelve  ounces  {283  to  Jj6.6  grm)  in  the  male,  and  from 
eight  to  ten  {26.^  to  28 J  grm)  in  the  female ;  but  much  depends 
upon  the  size  and  condition  of  the  body  generally.  As  a  rule, 
the  heart  gradually  increases  in  length,  breadth,  and  thickness 
from  childhood  to  old  age. 

Notice  two  longitudinal  grooves  {sulci)  on  the  front  and  back 
surfaces  of  the  heart,  which  extend  from  the  base  of  the  ventricles 
to  the  apex,  and  which  indicate  the  septum  between  the  two  ven- 
tricles ;  the  anterior  groove  lies  nearer  to  the  left  side,  the  poste- 
rior to  the  right  side  of  the  heart. 

A  circular  groove,  nearer  the  base,  marks  the  separation  be- 
tween the  auricles  and  ventricles.  In  the  circular  and  longitu- 
dinal furrows,  surrounded  by  more  or  less  fat,  run  the  coronary 
vessels,  the  nerves,  and  the  lymphatics. 

The  heart  is  a  double  hollow  muscular  organ ;  that  is,  it  is 
composed  of  two  hearts,  a  right  and  a  left,  separated  by  a  sep- 
tum, and  not  communicating  with  each  other  except  during 
uterine,  and  rarely  in  adult,  life.  Each  half  consists  of  two  cav- 
ities, an  auricle  and  a  ventricle,  which  communicate  by  a  wide 
orifice,  the  auriculo-ventricular  opening.  The  right  half  of  the 
heart  propels  venous  blood  to  the  lungs,  and  is  called  the  pul- 
monary ;  the  left  propels  arterial  blood  from  the  lungs  through- 
out the  body,  and  is  called  the  systemic.  These  two  hearts  are 
not  placed  apart,  because  important  advantages  result  from  their 
union.  By  being  enclosed  in  a  single  bag  they  occupy  less 
room  in  the  chest ;  and  the  action  of  their  corresponding  cavities 
being  precisely  synchronous,  their  fibres,  mutually  intermixing, 
contribute  to  their  mutual  support. 


214 


THE    RIGHT    AURICLE. 


The  cavities  of  the  heart  should  now  be  examined  in  the 
order  in  which  the  blood  circulates  through  them. 

Right  Auricle.  —  This  is  situated  at  the  right  side  of  the 
base  of  the  heart,  and  forms  a  quadrangular  cavity,  the  atrinvi 
or  sinus  venosus,  between  the  two  venae  cavae,  from  which  it 
receives  the  blood.  From  its  front  a  small  pouch  projects 
towards  the  left,  and  overlaps  the  root  of  the  aorta ;  this  part  is 
termed  the  appendix  anriciUce,  and  resembles  a  dog's  ear  in 
shape. 

Make  a  crucial  incision  over  the  anterior  surface  of  the  auricle, 
extending  one  prong  into  the  appendix.  The  interior  is  lined 
by  a  polished  membrane  called  the  endocardium,  and  is  every- 
where smooth  except  in  the  appendix,  where  the  muscular  fibres 
are  collected  into  bundles,  called,  from  their  resemblance  to  the 
teeth  of  a  comb,  mnsculi pectinati.  They  radiate  from  the  auricle 
to  the  edge  of  the  auriculo-ventricular  opening. 

The  following  objects  are  seen  on  opening  the  auricle :  — 

Superior  or  cephal  vena  cava.  Eustachian  valve. 

Inferior  or  caudal  vena  cava.  Coronary  valve. 

Coronary  sinus.  Annulus  ovalis. 

Auriculo-ventricular  opening.  Fossa  ovalis. 

Foramina  Thebesii.  Tubercle  of  Lovi^er. 

Musculi  pectinati. 

Examine  carefully  the  openings  of  the  two  vence  cavcE :  they 
are  not  directly  opposite  to  each  other  ;  the  siipenor  cava  opens 
into  the  auricle  on  a  plane  rather  in  front,  and  a  little  to  the 
left,  of  the  inferior,  so  that  its  orifice  is  opposite  to  the  auriculo- 
ventricular  opening.  The  inferior  cava,  after  passing  through 
the  tendinous  centre  of  the  diaphragm,  makes  a  slight  curve  to 
the  left  before  it  opens  into  the  lowest  part  of  the  auricle  ;  its 
direction  is  upwards  and  invv^ards,  so  that  the  stream  of  blood  is 
directed  towards  the  auricular  septum.  The  orifice  of  each 
vena  cava  is  nearly  circular,  and  surrounded  by  circular  mus- 
cular fibres  continuous  with  those  of  the  auricle. 

The  posterior  wall  of  the  auricle  is  formed  by  the  partition  be- 
tween the  auricles,  the  septum  auricularum.  Upon  this  septum, 
above,  and  to  the  left  of  thej^rifice  of  the  vena  cava  inferior,  is  an 
oval  depression  {fossa  ovalis),  bounded  by  a  prominent  border 
{annulus  ovalis).  This  depression  indicates  the  remains  of  the 
opening  {foramen  ovale)  through  which  the  blood  in  foetal  life 
passed  from  the  right  into  the  left  auricle.  After  birth  this 
opening  closes ;  but   if  the  closure  is  imperfect,  the  stream  of 


INTERIOR    OF    THE    RIGHT    AURICLE. 


215 


dark  blood  in  the  right  auricle  mixes  with  the  florid  blood  in  the 
left,  and  occasions  what  is  called  cyanosis.  A  valvular  commu- 
nication, however,  not  infrequently  exists  between  the  auricles 
in  this  situation  which  is  not  attended  with  indications  of  this 
disease. 

A  more  or  less  noticeable  fold  of  the  lining  membrane,  the 
Eustachian  valve,  may  be  seen  projecting  from  the  front  margin 
of  the  vena  cava  inferior  to  the  front  border  of  the  fossa  ovalis. 
It  is  placed  between  the  inferior  vena  cava  and  the  lower  margin 
of  the  annulus  ovalis.  Curved  in  shape,  it  passes  forwards  and 
ends  in  two  cornua  ;  of  which,  one  is  attached  to  the  annulus 
ovalis,  the  other  is  lost  on  the  wall  of  the  auricle.  It  consists 
of  a  reduplication  of  the  endocardium  and  contains  some  muscu- 
lar tissue.     It  is   the  remnant  of  a  valve,  which  was  of  con- 


Auriculo-ventricular 
orifice. 

Fossa  ovalis. 
Opening  of  the  coronary 
vein. 
Line  of  Eustachian  valve 


Fig.  78.  — DiAGR.\M  of  the  Intehior  of  the  Right  Auricle. 

siderable  size  in  foetal  life,  and  served  to  direct  the  current  of 
blood  from  the  vena  cava  inferior,  through  the  foramen  ovale, 
into  the  left  auricle. 

To  the  left  of  the  Eustachian  valve,  that  is,  between  its  re- 
mains and  the  auriculo-ventricular  opening,  is  the  orifice  of  the 
coronary  sinus.  The  sinus  is  about  an  inch  (2.5  cm.)  in  length 
and  receives  the  great  cardiac  vein,  the  posterior  cardiac  vein, 
and  the  oblique  vein  (of  Marshall),  and  will  nearly  admit  the 
end  of  the  little  finger.  It  is  surrounded  by  muscular  fibres, 
and  is  guarded  by  a  semicircular  fold  of  the  endocardium,  called 
the  valve  of  Thcbesius*  to  prevent  regurgitation  of  the  blood 
during:  the  auricular  contraction. 


*  This  valve  is  occasionally  double. 


2l6  '  THE    RIGHT    VENTRICLE. 

Here  and  there  upon  the  posterior  wall  of  the  auricle  may  be 
observed  minute  openings  for  the  small  veins  of  the  heart  {venae 
ininimcs  cordis),  called  foramina  TJicbesii ;  some  being  the 
orifices  of  small  veins  returning  blood  from  the  substance  of 
the  heart ;  others  being  simple  depressions  in  the  muscular 
tissue.  There  is  usually  one  larger  than  the  others  on  the 
septal  wall  below  the  superior  caval  opening  called  vetia  Galeni. 
To  the  left,  and  rather  in  front  of  the  orifice  of  the  vena  cava 
inferior,  is  the  aiiriculo-ventriciilar  opening,  guarded  by  the  tri- 
cuspid valve.  It  is  oval  in  form,  and  will  admit  the  passage  of 
three  fingers.  Lastly,  between  the  orifices  of  the  superior  and 
inferior  venae  cavae  is  a  rounded  elevation,  the  tubercle  of  Lower* 
(not  seen  in  the  diagram),  which  is  supposed  to  direct  the  cur- 
rent of  blood,  in  foetal  life,  from  the  superior  cava  to  the  auriculo- 
ventricular  opening. 

The  vinsculi  pcctinati  are  parallel  muscular  elevations  running 
across  the  inner  surface  of  the  auricular  appendix,  and  to  a  slight 
extent  also  of  the  sinus  venosus. 

Right  Ventricle. I  —  This  forms  the  right  border  and  about 
two-thirds  of  the  front  surface  of  the  heart.  Observe  th?'  the 
wall  of  the  ventricle  is  much  thicker  than  that  of  the  auncle. 
The  cavity  of  the  ventricle  is  conical,  with  base  upwards  and 
to  the  right.  Its  inner  wall  is  convex,  and  is  formed  by  the 
septum  ventriculorum.  The  upper  and  front  part  presents  a 
smooth  passage,  the  infiindibuhim  or  conns  arteriosus,  which 
leads  to  the  opening  of  the  pulmonary  artery.  It  is  situated  to 
the  left  and  in  front  of  the  auriculo-ventricular  opening,  and 
about  three-fourths  of  an  inch  (1 8  mm.)  higher. 

The  following  objects  are  seen  in  the  right  ventricle  :  — 

Columnae  carneae.  Auriculo-ventricular  opening. 

Chorda;  tendineae.  Pulmonary  opening  — 

guarded  by  the  tricuspid  and  semilunar  valves. 

From  its  walls  project  bands  of  muscular  fibres,  cohimnce  car- 
nccE,  of  various  length  and  thickness,  which  cross  each  other  in 
every  direction  ;  this  muscular  network  is  generally  filled  with 
coagulated  blood.     Of  these  columnae  carneae   there  are  three 

*  Most  distinct  in  quadrupeds. 

t  The  ventricle  can  best  be  opened  by  a  V  incision  made  by  introducing  the 
scissors,  and  cutting  parallel  with  the  anterior  ventricular  septum  into  the  pul- 
monary artery;  then  completing  the  V  by  cutting  parallel  with  the  postium  ven- 
tricular septem  up  to,  Intt  not  throui^h,  the  auriculo-ventricular  septum.  —  A.  H. 


TRICUSPID    VALVE.  21/ 

kinds  :  one  stands  out  in  relief  from  the  ventricle  ;  another  is 
attached  to  the  ventricle  by  its  extremities  only,  the  interme- 
diate portion  being  free  ;  a  third,  and  by  far  the  most  impor- 
tant set,  called  musculi  papillarcs,  is  fixed  by  one  extremity  to 
the  wall  of  the  ventricle,  while  the  other  extremity  gives  attach- 
ment to  the  fine  tendinous  cords,  cJiord(£  tendincce,  which  regu- 
late the  action  of  the  tricuspid  valve.  The  number  of  these 
musculi  papillares  is  equal  to  the  number  of  the  chief  segments 
of  the  valve ;  hence  there  are  three  in  the  right,  and  two  in  the 
left  ventricle.  Of  those  in  the  right  ventricle,  one  is  attached 
to  the  septum. 

There  are  two  openings  in  the  right  ventricle.  One,  the 
atiriailo-ventricnlar,  through  which  the  blood  passes  from  the 
auricle,  is  oval  in  form  and  placed  at  the  base  of  the  ventricle. 
It  is  surrounded  by  a  ring  of  fibrous  tissue,  to  which  is  attached 
the  tricuspid  valve. 

Tricuspid  Valve This   is  situated  at  the  right  auriculo- 

ventricular  opening,  and  consists  of  three  triangular  fiaps.  Like 
all  the  valves  of  the  heart,  it  is  formed  by  a  fold  of  the  lining 
membrane  (endocardiuni)  of  the  heart,  strengthened  by  fibrous 
tissue,  in  which  a  few  muscular  fibres  may  be  demonstrated. 
The  bases  of  the  valves  are  continuous  with  one  another,  so  that 
they  form  a  membranous  ring  between  the  auricle  and  ventricle, 
while  the  segments  project  into  the  cavity  of  the  right  ventricle. 
Of  its  three  flaps,  the  largest  or  anterior  is  so  placed,  that,  when 
not  in  action,  it  partially  covers  the  orifice  of  the  pulmonary 
artery  ;  another,  the  internal,  corresponds  with  the  inferior  wall 
of  the  ventricle  ;  the  third,  or  posterior,  rests  upon  the  septum 
ventriculorum. 

Observe  the  arrangement  of  the  tendinous  cords  which  regu- 
late the  action  of  the  valve.  First,  they  are  all  attached  to  the 
ventricular  surface  of  the  valve.  Secondly,  the  tendinous  cords 
proceeding  from  a  given  capillary  muscle  are  attached  to  the 
adjacent  halves  of  two  of  the  flaps  ;  consequently,  when  the 
ventricle  contracts,  and  the  papillary  muscle  also,  the  adjacent 
borders  of  the  flaps  will  be  approximated.  Thirdly,  to  insure 
the  strength  of  every  ])art  of  the  valve  the  tendinous  cords  are 
inserted  at  three  different  points  of  it  in  straight  lines  ;  accord- 
ingly, they  are  divisible  into  three  sets.  Those  of  the  first, 
which  are  three  or  four  in  number,  are  attached  to  the  base  of 
the  valve  ;  those  of  the  second,  from  four  to  six,  proceed  to  the 
middle  of  its  ventricular  surface;  those  of  the  third,  which  are 


2l8 


PULMONARY    VALVES. 


the    smallest    and    most    numerous,    are    attached    to    its    free 
margin.* 

Pulmonary  or  Semilunar  Valves These  are  three  semi- 
circular membranous  folds,  like  watch-pockets,  situated  at  the 
orifice  of  the  pulmonary  artery.  They  are  attached  by  their 
convex  borders  to  the  root  of  the  artery  ;  their  free  edges  look 
upwards,  and  present  a  festooned  border,  in  the  centre  of  which 
is  a  small  cartilaginous  body,  called  the  nodiilus  or  corpus  Arantii. 
The  use  of  these  bodies  is  plain.     Since  the  valves  are  semilu- 


FiG.  79.  —  Anatomy  of  the  Heart.  —  Right  Side. 

I.  Cavity  of  right  auricle.  2.  Appendix  auncula;  in  its  cavity  are  seen  the  musculi  pectinati. 
3.  Superior  vena  cava,  opening  into  the  upper  part  of  the  right  auricle.  4.  Inferior  vena  cava. 
5.  Fossa  ovalis  ;  the  prominent  ridge  surrounding  it  is  the  annulus  ovalis.  6.  Eustachian  valve. 
7.  Opening  of  the  coronary  vein.  8.  Coronary  valve.  9.  Entrance  of  the  auriculo-ventricular 
opening.  Between  tlie  figures  i  and  g,  two  or  three  foramina  Thebesii  are  seen.  a.  Ri^ht  ven- 
tricle, li,  c.  Caviiy  of  right  ventricle,  on  the  walls  of  which  columna;  carnea;  are  seen;  c  is  placed 
in  the  channel  leading  upwards  to  the  pulmonary  artery,  d.  e./.  Tricuspid  valve;  e  is  placed  in 
the  anterior  flap,  /on  the  right  flap.  g.  Long  columna  carnea.  to  the  apex  of  which  the  anterior 
and  right  flaps  are  C(jnnected  by  chords  tendinex-.  //.  The  "  long  rnoderator  band."  /.  The  two 
column.X'  cameie  of  the  right  flap.  k.  Attachment  by  chorda;  tendinea:  of  the  left  limb  of  the 
anterior  flap.  /,  I.  Chord.-E  tendineae  of  the  more  fixed  jiortion  of  the  valve,  in.  Valve  of  the 
pulmonary  artery.  ;/.  Apex  of  left  appendix  auriculx-.  o.  Left  ventricle.  /.  Ascending  aorta. 
q.  Its  transverse  portion  with  the  three  arterial  trunks  which  arise  from  the  arch.  r.  iJescend- 
ing  aorta. 

*  The  best  mode  of  showing  the  action  of  the  valve  is  to  introduce  a  glass 
tube  into  the  pulmonary  artery,  and  then  to  pour  water  through  it  into  the  ventri- 
cle until  the  cavity  is  quite  di.stended.  By  gently  squeezing  the  ventricle  in  the 
hand,  so  as  artificially  to  imitate  its  natural  contraction,  the  tricu.spid  valve  will  flap 
back  like  a  flood-gate,  and  close  the  auriculo-ventricular  opening.  In  this  way  one 
can  understand  how,  when  the  ventricle  contracts,  the  blood  catches  the  margin  of 
the  valve,  and  by  its  pressure  gives  it  the  pro])er  distention  and  figure  requisite  to 
block  u])  the  aperture  into  the  auricle.  It  is  obvious  that  tiie  tendinous  cords  will 
prevent  the  valve  from  flapping  back  into  the  auricle;  and  tliis  purpose  is  assisted 
by  the  papillary  musdes,  wliich  nicely  adjust  the  degree  of  tension  of  the  cords  at 
a  time  when  they  would  otherwise  be  too  much  slackened  by  the  contraction  of  the 
ventricle. 


PULMONARY    VALVES.  219 

nar,  when  they  fall  together  they  would  not  exactly  close  the 
artery  ;  there  would  be  a  space  of  a  triangular  form  left  between 
them  in  the  centre,  just  as  there  is  when  we  put  the  thumb,  fore, 
and  middle  fingers  together.  This  space  is  filled  up  l)y  these 
nodules,  so  that  the  closure  becomes  complete. 

The  valves,  two  anterior  and  one  posterior,  are  composed  of 
folds  of  the  endocardium,  or  lining  membrane  of  the  heart.  Be- 
tween the  folds  is  a  thin  layer  of  fibrous  tissue,  which  is  pro- 
longed from  the  fibrous  ring  at  the  orifice  of  the  artery.  This 
layer  of  fibrous  tissue,  however,  reaches  the  free  edge  of  the 


Fig.  80.  —  Anatomy  of  the  Heart.  —  Left  Side. 
I.  Cavity  of  left  auricle.  2.  Cavity  of  the  appendix  auriculs,  near  the  apex  of  which  are  seen 
musciili  pectinati.  3.  Opening  of  the  two  right  pulmonary  veins.  4.  The  sinus  into  which 
the  left  pulmonary  veins  open.  5.  Left  pulmonary  veins.  6.  Auriculo-ventricular  opening, 
7.  Coronary  vein,  lying  in  the  auriculo-veniricular  groove.  8.  Left  ventricle.  9,9.  Cavity  of 
the  left  ventricle;  the  figures  rest  on  the  septum  ventriculorum.  a.  Mitral  valve;  its  flaps  are 
connected  by  chordiE  tendineiE  to  ^,  i^,  ^.  Column.^  carnea;.  c,c.  Fixed  columns?  carnea?,  form- 
ing part  of  the  internal  surface  of  the  ventricle.  ./.  Arch  of  the  aorta,  from  the  summit  of  which 
the  three  trunks  (arterial)  are  seen.  e.  Pulmonary  artery,  f.  Obliterated  ductus  arteriosus. 
g.  Left  pulmonary  artery.     /;.   Right  ventricle.     /.  Point  of  the  appendix  of  right  auricle. 

valve  at  three  points  only :  namely,  at  the  centre,  or  corpus 
Arantii,  and  at  each  extremity.  Between  these  points  it  stops 
short,  and  leaves  a  crescent-shaped  portion  of  the  valve,  which 
is  thinner  than  the  rest,  and  consists  of  the  endocardial  mem- 
brane. This  crescent-shaped  portion,  called  the  lunula,  is  not 
wholly  without  fibrous  tissue  ;  a  thin  tendinous  cord  runs  along 
its  free  edge,  to  give  it  additional  strength  to  resist  the  pressure 
of  the  blood.  Behind  each  of  the  valves  the  artery  bulges  and 
forms    three    slight    dilations    called    the   sinuses  of    Valsalva. 


220  LEFT    AURICLE. 

These,  we  shall  presently  see,  are  more  marked  at  the  orifice  of 
the  aorta. 

The  action  of  these  valves  is  evident.  During  the  contrac- 
tion of  the  ventricle  the  valves  lie  against  the  side  of  the  artery, 
and  offer  no  impediment  to  the  current  of  blood  ;  during  its  dila- 
tation the  elasticity  of  the  distended  artery  would  force  back  the 
column  of  blood,  but  that  the  valves,  being  caught  by  the  reflu- 
ent blood,  bag,  and  fall  together  so  as  to  close  the  tube.  The 
greater  the  pressure,  the  more  complete  is  the  closure.  The 
coats^of  the  artery  are  very  elastic  and  yielding,  while  the  valve, 
like  the  circumference  to  which  it  is  attached,  is  quite  unyield- 
ing ;  consequently,  when  the  artery  is  distended  by  the  impulse 
of  the  blood,  its  w-all  is  removed  from  the  contact  of  the  free 
margin  of  the  valves,  and  these  are  the  more  readily  caught  by 
the  regurgitating  motion  of  the  blood.  The  force  of  the  reflux 
is  sustained  by  the  tendinous  part  of  the  valves,  and  by  the 
muscular  wall  of  the  ventricle  (probably  in  a  state  of  contrac- 
tion). The  valves  are  capable  of  sustaining  a  weight  of  sixty- 
three  pounds  before  they  give  way.  The  thinner  portions 
{hinulcB)  become  placed  so  as  to  lie  side  by  side,  each  one  with 
that  of  the  adjacent  valve.  This  may  be  demonstrated  by  fill- 
ing the  artery  with  water. 

Left  Auricle.  —  This  is  situated  at  the  left  side  and  posterior 
part  of  the  base  of  the  heart,  and  is  somewhat  smaller  than  the 
right  auricle.  It  consists,  like  the  right  auricle,  of  a  cavity  — 
the  simis  vcnosiis  —  and  the  auricular  appendix.  It  is  quadri- 
lateral, and  receives  the  four  pulmonary  veins,  two  on  either 
side,  which  return  the  oxygenated  blood  from  the  lungs.  From 
its  upper  and  left  side,  the  auricular  appendix  projects  towards 
the  right,  curling  over  the  root  of  the  pulmonary  artery.  The 
auricle  should  be  opened  by  a  horizontal  incision  along  the 
ventricular  border  of  the  auricle,  and  another  should  be  made 
upwards  from  the  centre  of  the  first  incision. 

The  interior  of  the  atrium  is  smooth  and  flat,  but  in  the 
appendix  there  are  numerous  raised  muscular  bands,  the  musculi 
pectinati.  The  interior  presents  the  following  objects  for 
examination :  — 

The  orifices  of  the  four  pulmonary  veins. 
The  auriculo-ventricular  opening. 
The  musculi  pectinati. 

The  openings  of  the  pulmonary  veins  are  seenwn  the  posterior 
wall,  two  on  the  right  side  (sometimes  three),  and  two  on  the 


LEFT    VENTRICLE.  221 

left  side.  They  are  not  guarded  by  valves.  Upon  the  septum 
between  the  auricles  is  a  semilunar  depression,  indicating  the 
remains  of  the  foramen  ovale.  The  atiriculo-ventricidar  opening, 
situated  at  the  lower  and  front  part  of  the  auricle,  is  smaller 
than  that  of  the  right  side,  and  somewhat  oval.  Its  long  axis 
is  nearly  transverse,  and,  in  the  adult,  will  admit  the  passage  of 
two  fingers.  The  ninsculi  pectinati  are  also  smaller  and  fewer 
than  in  the  right  auricle. 

Left  Ventricle.*  —  This  occupies  the  left  border,  and  forms 
the  apex  of  the  heart.  One-third  of  it  only  is  seen  on  the 
anterior  surface,  the  rest  being  on  the  posterior.  To  examine 
the  interior,  raise  a  triangular  flap,  with  the  apex  below,  from 
its  front  wall.  Observe  that  its  wall  is  about  three  times  as 
thick  as  that  of  the  right  ventricle,  and  that  this  thickness 
gradually  diminishes  towards  the  apex.  The  interior  of  the 
left  ventricle  presents  the  following  objects  for  examination  :  — 

Auriculo-ventricular  opening.  Auriculo-ventricular  or  mitral  valves. 

Aortic  opening.  Semilunar  valves. 

Columnae  cameas. 

These  parts  so  closely  resemble  that  of  the  right  that  there  is 
no  necessity  to  describe  them  in  detail.  The  auriculo-ventricu- 
lar valve  consists  of  two  flaps  ;  hence  its  name,  mitral  or 
bicuspid.  The  larger  of  these  flaps  is  placed  between  the  aortic 
and  auriculo-ventricular  orifices.  There  are  only  two  miisculi 
papillares :  one  attached  to  the  anterior,  the  other  to  the  poste- 
rior wall  of  the  ventricle.  They  are  thicker,  and  their  cJiordcB 
tendinecB  stronger,  than  those  of  the  right  ventricle,  but  their 
arrangement  is  precisely  similar.  From  the  upper  and  back 
part  of  the  ventricle  a  smooth  passage  leads  to  the  orifice  of  the 
aorta.  This  orifice  is  placed  in  the  groove  between  the  two 
auricles,  and  somewhat  in  front  and  to  the  right  side  of  the 
left  auriculo-ventricular  opening.  The  two  orifices  are  close 
together,  and  only  separated  by  the  larger 'flap  of  the  mitral 
valve.  The  aortic  orifice  is  guarded  by  three  semilunar  valves, 
of  which  the  arrangement,  structure,  and  mode  of  action  are 
similar  to  those  of  the  pulmonary  artery.  Their  framework  is 
proportionally  stronger,  consistently  with  the  greater  strength 
of  the  left  ventricle,  and  the  greater  impulse  of  the  blood.  In 
the  sinuses  of  Valsalva  are  observed  the  orifices  of  the  two 

*  Similar  incision  should  be  made  as  indicated  for  the  right  ventricle  (p.  216). 
—  A.  H. 


222  CORONARY    ARTERIES. 

coronary  arteries  ;  the  left  arising  from  the  sinus  behind  the  left 
posterior  segment  ;  the  right  from  behind  the  anterior  segment. 

Size  of  the  Auriculo-ventricular  and  Arterial  Openings. 
—  The  circumferences  of  the  four  orifices  are  as  follows  :  that 
of  the  tricuspid  orifice,  4.74  inches  [II.8  cin.)  ;  that  of  the  mitral, 
4  inches  {10  cm.)  ;  that  of  the  pulmonary,  3.55  inches  {S.y  cm.)  ; 
and  that  of  the  aortic,  3.14  inches  {J.y  cm.).* 

Coronary  Arteries. —  The  heart  is  supplied  with  blood  by 
the  two  coronary  arteries,  a  right  or  posterior,  and  a  left  or 
anterior.  They  are  about  the  size  of  a  crow's  quill.  Both  arise 
from  the  aorta  just  above  the  free  margins  of  the  two  semi- 
lunar valves,  and  thus  always  allow  the  passage  of  blood  ;  both 
run  in  the  furrows  on  the  surface  of  the  heart ;  both  are  accom- 
panied by  the  cardiac  nerves  and  by  lymphatics. 

The  anterior  or  left  coronary  artery,  the  smaller  of  the  two,  arises  from  behind 
the  left  posterior  valve  of  the  aortic  orifice.  It  appears  between  the  pulmonary 
artery  and  the  appendix  of  the  left  auricle,  and  then  divides  into  two  branches : 
one  which  seems  the  continuation  of  the  main  trunk  and  runs  down  the  inter-ven- 
tricular furrow  on  the  anterior  surface  of  the  heart  to  the  apex  ;  the  other  passes 
transversely  to  the  left,  in  the  left  auriculo-ventricular  groove  to  the  back  of  the 
heart. 

The  posterior  or  right  coronary  artery  arises  from  behind  the  anterior  cusp  of 
the  aortic  opening,  and  descends  obhquely  between  the  pulmonary  arteiy  and  the 
appendix  of  the  right  auricle.  It  then  turns  to  the  right  in  the  groove  between  the 
right  ventricle  and  auricle  to  the  back  of  the  heart,  where  it  divides  into  two 
branches  ;  one  of  which  descends  in  the  posterior  inter-ventricular  furrow  towards 
the  apex  of  the  heart ;  the  other,  which  appears  to  be  the  continuation  of  the  main 
trunk,  runs  in  the  left  auriculo-ventricular  groove.  Besides  these  branches,  the 
right  coronary  gives  off  a  large  branch  which  runs  along  the  free  border  of  the 
right  ventricle. 

Thus,  the  leading  trunks  of  the  coronary  arteries  run  in  the 
furrows  of  the  heart,  usually  surrounded  by  fat.  Their  numer- 
ous branches  supply  the  walls  of  the  auricles  and  ventricles, 
and  their  terminations  communicate  with  each  other. 

Coronary  Veins  and  Sinus. —  The  vein  which  corresponds 
with  the  anterior  cpronary  artery  ascends  in  the  anterior  inter- 
ventricular sulcus,  and  then  curves  round  the  left  side  of  the 
heart  in  the  left  auriculo-ventricular  groove,  where  it  takes  the 
name  of  the  great  cardiac  vein.  This  vein  soon  dilates  into  a 
large  trunk,  the  coronary  sinus,  which  opens  at  the  back  of  the 
right  auricle  below  the  Eustachian  valve. 

Another  vein,  known  as  the  posterior  cardiac,  ascends  along  the  posterior  inter- 
ventricular groove,  to  open  by  valved  orifices  into  the  coronary  sinus  ;  while  others, 

♦  Dr.  Peacock,  Croonian  Lectures,  1865. 


THE    HEART.  223 

the  anterior  cardiac  veins,  three  or  four  in  number,  are  seen  running  up  on  the 
anterior  surface  of  the  right  ventricle  to  terminate  directly  in  the  right  auricle. 

The  vencB  TJicbcsii  transmit  the  blood  directly  from  the 
muscular  structure  into  the  right  auricle  by  small  apertures,  the 
foramina  Thebesii.  The  coronary  sinus  is  about  an  inch  {2.^  cm.) 
in  length,  and  receives  the  great  cardiac  vein,  the  posterior 
cardiac  vein,  and  the  oblique  vein  of  Marshall,  placed  on  the 
posterior  surface  of  the  left  auricle.  Its  orifice  in  the  right 
auricle  is  guarded  by  a  semilunar  valve  {valve  of  Thcbcshis)  to 
prevent  regurgitation  of  the  blood.  It  is  covered  and  more  or 
less  supported  in  its  course  by  muscular  fibres  passing  from  one 
auricle  to  the  other. 

The  lymphatics  of  the  heart  pass  mainly  into  a  trunk  which  runs  in  the  ante- 
rior inter- ventricular  groove,  and  then,  passing  into  the  glands  between  the  aorta 
and  trachea,  open  into  the  right  lymphatic  duct ;  other  smaller  lymphatics  pass 
into  the  thoracic  duct. 

The  nerves  are  derived  from  the  cardiac  plexuses,  which  have  been  already 
described,  p.  210. 

Fibrous  Rings  of  the  Heart.  —  What  may  be  termed  the  fibrous  skeleton  of 
the  heart  consists  of  four  rings,  which  surround,  respectively,  the  four  orifices  at 
its  base ;  namely,  the  two  auriculo-ventricular,  the  aortic,  and  the  pulmonary. 
These  rings  give  attachment  by  their  external  circumference  to  the  muscular  fibres 
of  the  heart,  and  from  their  internal  circumference  send  fibrous  prolongations  to 
form  the  framework  of  the  several  valves.  The  skeleton  is  strongest  just  in  the 
triangular  interspace  between  the  aortic  and  the  two  auriculo-ventricular  orifices 
(letter  A  in  Fig.  Si).  In  some  animals,  as  in  the  ox  and  the  elephant,  there  is  here 
an  irregularly  triangular  bone,  known  as  the  os  cordis. 

The  relative  position  of  these  rings  is  best  seen  by  removing  the  auricles  and 
the  great  vessels  at  the  base  of  the  heirt  —  leaving  the  several  valves,  and  looking 
at  them  from  above,  as  shown  in  the  diagram.  The  pulmonary  ring  is  on  the 
highest  level,  and  nearest  to  the  sternum ;  below  it,  is  the  aortic  ring  lying  between 
and  in  front  of  the  auriculo-ventricular  rings,  which  are  on  the  lowest  level. 

Attachment  of  the  Large  Arteries  to  the  Ventricles. — 

The  fibrous  rings  at  the  arterial  orifices  present  three  festoons 
with  their  concavities  directed  upwards.  These  give  attach- 
ment, above,  to  the  middle  coat  of  the  artery ;  below,  to  the 
muscular  fibres  of  the  ventricles  ;  and,  internally,  to  the  fibrous 
tissue  of  the  valves.  The  vessels  are  also  connected  to  the 
heart  by  the  serous  layer  of  the  pericardium,  and  by  a  continua- 
tion of  the  lining  membrane  of  the  ventricle. 

Epicardium.  —  This,  the  visceral  layer  of  the  pericardium, 
closely  invests  the  external  surface  of  the  heart,  and  presents 
the  usual  appearances  of  a  visceral  serous  membrane. 

Endocardium.  —  This  smooth  membrane  lining  the  cavities 
of  the  heart  resembles  the  visceral  layer  of  the  pericardium,  and 
is  continuous  with  the  inner  coat  of  the  blood-vessels.     It  may  be 


224 


MUSCULAR    FIBRES    OF    THE    HEART. 


easily  stripped  off,  and  is  thin  and  semi-transparent,  thicker  in  the 
left  than  in  the  right  cavities,  thickest  of  all  in  the  left  auricle. 

Arrangement  of  the  Muscular  Fibres  of  the  Auricles.  —  The  fibres  of  the 
auricles  are  distinct  from  those  of  the  ventricles.  They  consist  of  a  superficial 
layer  common  to  both  cavities,  and  a  deeper  layer  proper  to  each.  The  superficial 
fibres  run  transversely  across  the  auricles,  and  are  most  marked  on  the  anterior 
surface  ;  some  pass  into  the  inter-auricular  septum.  Of  the  deeper  fibres,  some 
are  ainuilar  and  surround  the  auricular  appendages  and  the  entrance  of  the  great 
veins,  upon  which  a  few  may  be  traced  for  a  short  distance;  others,  looped^  run 
over  the  auricles,  and  are  auached  in  front  and  behind  to  the  auriculo-venlricular 
rings. 

Arrangement  of  the  Muscular  Fibres  of  the  Ventricles.  —  Speaking  gen- 
erally, it  may  be  said  that  the  right  and  left  ventricles  of  ihe  heart  are  two  conical 
muscular  sacs,  enclosed  in  a  third,  which  not  only  envelops  them,  but  is  reflected 


Fig.  8t  . — Diagram   op   the    Relative    Position   of   the   Valves   of   the   Heart,   seen 

FROM  above. 

A  is  placed  on  the  triangular  interval  where  the  fibrous  skeleton  is  the  tliickest. 


into  the  interior  of  both,  at  their  apices,  so  as  to  line  their  cavities.  All  the  mus- 
cular fibres  are  attached  by  one  end  1o  the  fibrous  rings  of  the  orifices,  and,  by  the 
other  end,  after  a  more  or  less  spiral  course,  they  reach  the  rings  again,  either 
directly  or  through  the  medium  of  the  chordae  tendinere  and  valves. 

The  external  or  superficial  fibres  pass  from  the  base,  where  they  are  attached 
to  the  auriculo-ventricular  ring.s,  to  the  apex.  This  layer  is  thin  in  front,  but  be- 
hind it  is  better  marked,  and  here  the  fibres  do  not  pass  into  the  septum,  but  over 
it,  while  in  front  they  pass  over  the  anterior  septum,  only  at  the  base  and  apex  of 
the  ventricle.  The  fibres  nin  more  or  less  spirally  towards  the  apex,  where  they 
form  a  whorl  and  pass  into  the  left  ventricle,  so  as  to  form,  in  part  the  innermost 
vertical  mu.scular  layer,  in  part  the  fleshy  columns  of  its  cavity.  The  superficial 
anterior  fibres  pass  backwards  to  the  left,  and  form,  Ijehind,  the  posterior  papillary 
muscle;  and,  on  the  other  hand,  the  superficial  fibres  pass  over  the  right  side  of 
the  heart  and  constitute  the  anterior  ])a])illary  muscle. 

The  remaining  fibres  of  the  left  ventricle,  which  constitute  its  chief  thickness, 
are  attached  to  the  fibrous  rings  at  the  base  of  the  heart.    They  pass,  more  or  less 


FCETAL    CIRCULATION.  225 

obliquely,  in  the  posterior  and  anterior  walls,  and  entering  the  lower  end  of  the 
sei)tuin  ])ass  in  three  different  directions:  otie  set,  upwards  in  the  septum  to  he  at- 
tached to  the  fibrous  tissue  in  the  triangular  interspace;  z.  second  set  pass  through 
the  septum  to  form  the  posterior  wall  of  the  right  ventricle  and  its  posterior  papil- 
lary muscle;  while  the  third  set  take  a  transverse  circular  course  in  the  left  ven- 
tricle, some  of  its  fibres  being  continuous  with  those  of  the  right  ventricle. 

The  fibres  of  the  right  ventricle  are  arranged  on  a  plan  similar  to  that  of  the 
left  ventricle,  of  which  it  may  be  considered  an  appendage.  The  fibres,  which  cor- 
respond to  those  forming  the  chief  thickness  of  the  left  ventricle,  are  similarly 
arranged  into  an  interior,  middle,  and  posterior  set  :  the  anterior  pass  backwards 
into  the  septum  to  reach  the  posterior  wall  of  the  left  ventricle,  and  interlace  in  the 
septum  with  the  posterior  set,  which  pass  foi-v\ards  in  the  septum  to  the  front  wall 
of  the  left  ventricle  ;  the  middle  set  come  chiefly  from  the  outer  wall  of  the  right 
ventricle,  deep  down  at  the  lower  part  of  the  septum,  and  then  ascend  to  be  at- 
tached to  the  fibro-caitilage.  Besides  these  there  are  more  or  less  numerous 
annular  fibres  encircling  the  right  ventricle.* 

Thickness  of  the  Cavities.  —  The  average  thickness  of  the 
right  auricle  is  about  rV  of  an  inch  {2  vim)  ;  that  of  the  left  \ 
of  an  inch  (J  mm).  The  average  thickness  of  the  right  ventri- 
cle at  its  thickest  part  —  i.e.,  the  base  —  is  about  \  of  an  inch 
{if.  mm) ',  that  of  the  left  ventricle  at  its  thickest  part  —  i.e., 
the  middle  —  is  about  half  an  inch  {12.^  mm).  In  the  female 
the  average  is  less. 

Peculiarities  of  the  Foetal  Circulation. — The  heart  and 
the  circulation  of  the  foetus  differ  from  that  of  the  adult  in  the 
following  points  :  — 

1.  The  Eustachian  valve  is  well  developed  as  a  crescentic 
fold  which  guides  the  current  of  blood  from  the  inferior  vena 
cava  through  the  right  auricle  into  the  foramen  ovale. 

2.  Thefoivjuen  ovale  is  widely  open  up  to  the  fourth  month, 
after  which  a  septum  grows  up  from  the  lower  border  of  the  left 
side,  so  that  at  the  sixth  month  the  blood  can  only  pass  in  the 
onward  direction  into  the  left  auricle. 

3.  The  right  and  left  pttlmoiiary  arteries  are  very  small  and 
ill  developed,  so  as  to  admit  very  Httle  blood  to  the  lungs. 

4.  The  ductus  arteriosus,  from  the  commencement  of  the  left 
pulmonary  artery  to  the  aorta,  is  widely  open. 

5.  T\\Q  hypogastric  or  nmbilical  arter'ies,  hr2ir\c\\es  of  the  an- 
terior division  of  the  internal  iliac,  emerge  through  the  umbili- 
cus and  pass  to  the  placenta,  so  that  the  impure  blood  may  be 
oxygenated. 

*  There  are  other  accounts  given  of  the  arrangements  of  the  muscular  structure 
of  the  heart,  and  that  given  by  Pettigrew  is  one  which  is  adopted  by  many  of  the 
best  anatomists.  For  further  information  on  this  subject  consult  Pettigrew,  Philo- 
soph.  Transactions,  1864;  Dr.  Sibson,  ATedical  Anatomy,  1S69;  Winckler,  Mill- 
lev's  Arcliiv,  1865  ;   Quain's  Anatomy,  vol.  ii.  p.  495,  1882. 


226 


FQ^TAL    CIRCULATION, 


6.  The  umbilical  vein   returns  the  pure  blood  partly  to  the 
liver,  and  partly  through  the  — 

7.  Ductus  vcnosus  into  the  inferior  vena  cava. 

8.  The  rigJit  and  left  ventricles  are  of  equal  thickness,  because 
they  have  equal  work  to  perform. 

FCETAL    CIRCULATION. 


Circulation  of  the  Blood  in  the  FcEtus.  —  Arterial  blood  is  brought  from  the 
placenta  by  the  umbilical  vein  (Fig.  82),  and  enters  at  the  umbilicus,  whence  it 
passes  to  the  under  surface  of  the  liver.  Here  it  gives  off  some  branches  to  the 
left  lobe,  and  others  to  the  lobulus  Spigelii  and  lobulus  quadratus,  which  eventually 
return  their  blood  into  the  inferior  vena  cava.     At  the  transverse  fissure  it  divides 


SUP*^  V.  c 


FORAMEN  OVALE 


DOCTl/a 
ARTERIOSUS 


LEFT   PULNI* 
ARTERY. 


PLAC  ENTA 

Fig.  82. —  Scheme  oh  the  Fcetal  Circulation. 


STRUCTURE    OF    THE    LUNGS.  22J 

into  two  branches  —  one,  the  smaller,  termed  the  ductus  venosus,  passes  straight 
to  enter  into  the  inferior  vena  cava,  having  previously  joined  the  left  hepatic  vein; 
the  other,  or  right  division,  joins  the  vena  portse,  and,  after  ramifying  in  the  right 
lobe  of  the  liver,  returns  its  blood  through  the  hepatic  veins  into  the  inferior  vena 
cava. 

From  the  inferior  vena  cava,  which  thus  receives  its  blood  from  three  sources, 
the  blood  enters  the  right  auricle,  and  the  stream  (directed  by  the  Eustachian  valve) 
flows  through  the  foramen  ovale  into  the  left  auricle,  where  it  becomes  mingled 
with  a  little  blood,  which  is  returned  from  the  pulmonary  veins.  P'rom  the  'eft 
auricle  it  runs  through  the  left  auriculo-ventricular  opening  into  the  left  ventricle, 
and  thence  through  the  aorta  into  the  great  vessels  of  the  head  and  upper  extremi- 
ties (only  a  small  quantity  passing  into  the  descending  thoracic  aorta),  which  are 
thus  supplied  by  almost  pure  blood.  From  the  head  and  upper  hmbs  the  blood 
returns  (impure)  through  the  superior  vena  cava  into  the  right  auricle,  whence, 
mixed  with  a  small  quantity  derived  from  the  inferio  cava,  it  passes  into  the  right 
ventricle.  From  the  right  ventricle  the  blood  passes  through  the  pulmonai^  arteiy 
and  the  ductus  arteriosus  into  the  commencement  of  the  descending  aorta,  only  a 
very  small  quantity  of  it  being  distributed  to  the  lungs  ;  the  lungs  are  in  the  fcetus 
almost  solid  organs,  and  the  blood  distributed  to  them  is  returned  by  the  pul- 
monary veins  into  the  left  auricle.  The  blood  which  passes  into  the  de.scending 
aorta,  through  the  ductus  arteriosus,  is  mingled  with  the  small  amount  coming 
through  the  arch,  and  is  then  conveyed  through  the  abdominal  aorta  into  the  iliac 
arteries ;  part  is  transmitted  through  the  umbilical  arteries  (branches  of  the  inter- 
nal iliac  arteries)  to  the  placenta  to  become  re-oxygenated ;  part  passes  into  the 
lower  extremities  through  the  external  iliac  and  femoral  arteries. 

Changes  in  the  Circulation  at  Birth.  —  The  following  changes  take  place  in 
the  circulation  after  birth  :  — 

1.  The  titnbilicns  vein  becomes  obliterated  from  the  second  to  the  fifth  day 
after  birth,  and  subsequently  forms  the  round  ligament  of  the  liver. 

2.  The  ductus  venosus  also  becomes  closed  about  the  same  period,  and  may  be 
traced  as  a  thickened  cord  in  the  fissure  of  the  ductus  venosus. 

3.  The  foramen  ovale  becomes  closed  from  the  sixth  to  the  tenth  day  ;  but  not 
infrequently  a  small,  indirect  valvular  communication  may  be  found  forming  a 
communication  between  the  two  auricles. 

4.  The  ductus  arteriosus  contracts  immediately  after  birth,  and  becomes  closed 
from  the  sixth  to  the  tenth  day.  It  eventually  forms  a  fibrous  cord  connecting  the 
left  pulmonary  artery  wth  the  aorta,  the  left  recurrent  laryngeal  nerve  winding 
round  its  left  border.* 

5.  The  pulmonary  arteries  enlarge  and  convey  venous  blood  to  the  lungs. 
These  organs  during  foetal  life  receive  only  a  small  quantity  of  blood  from  these 
arteries. 

6.  The  hypogastric  arteries  become  obliterated  on  the  fourth  or  fifth  day  after 
birth. 

STRUCTURE    OF   THE   LUNGS. 

The  lungs  are  very  vascular,  spongy  organs  in  which  the 
blood  is  oxygenated  by  exposure  to  atmospheric  air.  Their  sit- 
uation and  shape  have  been  described  {p.  177).     We  must  now 

*  The  initial  cause  of  the  closure  of  the  ductus  arteriosus  has  been  attributed 
to  the  contraction  of  the  mu.scular  fibres  reflected  to  the  fibrous  pericardium  from 
the  diaphragm,  the  upper  portion  of  the  pericardium  being  held  firmly  through  the 
attachment  of  the  cervical  fascia  to  it  and  the  first  rib,  thereby  preventing  the 
descent  of  the  central  tendon  of  the  diaphragm.  The  muscular  fibres  act  as 
tensors  of  the  pericardium,  which  embrace  the  duct  in  question.     (A.  H.) 


228  THE    TRACHEA. 

examine  the  trachea,  the  common  air-passage  to  both  lungs,  and 
then  trace  this  tube  downwards  to  its  bifurcation  into  the  two 
bronchi,  which,  with  their  minute  subdivisions,  form  the  main 
structure  of  the  lungs. 

Trachea.  —  This  is  a  partly  cartilaginous,  partly  membra- 
nous tube,  and  is  situated  in  the  middle  line.  It  extends  from 
the  cricoid  cartilage,  i.e.,  opposite  the  upper  border  of  the  sixth 
cervical  vertebra,  to  the  third  thoracic  vertebra,  where  it  divides 
into  two  tubes,  the  right  and  left  bronchus  —  one  for  each  lung. 
Its  length  is  from  four  and  a  half  to  five  inches  {1 1. 2  cm.  to 
72.5  cm),  and  its  width  from  two-thirds  to  five-sixths  of  an  inch 
(/6  to  20  mm.)  ;  but  these  measurements  vary  according  to  the 
age  and  sex  of  the  patient,  and  the  capacity  of  the  lungs.  The 
trachea  is  surrounded  by  a  quantity  of  loose  connective  tissue, 
so  as  to  allow  of  its  free  mobility.  It  is  kept  permanently  open 
by  a  series  of  incomplete  cartilaginous  rings,  from  sixteen  to 
twenty  in  number,  which  extend  round  the  anterior  two-thirds 
of  its  circumference.  These  rings  are  deficient  at  the  posterior 
part  of  the  tube,  where  it  is  completed  by  a  fibro-muscular  mem- 
brane. This  deficiency  allows  the  trachea  to  enlarge  or  diminish 
its  calibre  ;  and  for  this  purpose  the  membranous  part  of  the 
tube  is  provided  with  unstriped  muscular  fibres  which  can  ap- 
proximate the  ends  of  the  rings. 

The  relations  of  the  trachea  to  the  surrounding  parts  should 
be  considered,  first,  in  the  neck,  and  then  within  the  thorax. 

In  the  neck,  it  has,  in  front  of  it,  the  isthmus  of  the  thyroid 
body,  the  sterno-hyoid  and  sterno-thyroid  muscles,  the  inferior 
thyroid  veins,  two  layers  of  the  deep  cervical  fascia,  the  arteria 
thyroidea  ima,  if  present,  and  (at  the  root  of  the  neck)  the  in- 
nominate and  left  common  carotid  arteries.  Laterally,  it  is  in 
relation  with  the  lobes  of  the  thyroid  body,  the  common  carotid 
arteries,  the  recurrent  laryngeal  nerves,  and  the  inferior  thyroid 
arteries.  Behind  it  is  the  oesophagus,  inclining  slightly  to  the 
left. 

In  the  chest  the  trachea  is  contained  in  the  superior  medias- 
tinum, and  has,  'm  fro7it  of  it,  the  manubrium  sterni,  the  origins 
of  the  sterno-hyoid  and  thyroid  muscles,  the  left  brachio-cephalic 
vein,  the  first  parts  of  the  innom.inate  and  left  common  carotid 
arteries,  the  transverse  portion  of  the  arch  of  the  aorta,  and  the 
deep  cardiac  plexus.  On  the  right  s\(\*i  are  the  pleura  and  right 
pneumogastric  nerve  ;  on  the  left,  the  pleura,  the  left  carotid, 
the  left  pneumogastric,  cardiac,  and  recurrent  laryngeal  nerves. 


BRONCHI,    RIGHT    AND    LEFT. 


229 


Bronchi,  Right  and  Left.  —  The  two  bronchi di^QX  in  length, 
direction,  and  diameter.  The  J'ight,  wider  but  shorter  than  the 
left,  is  about  an  inch  {2.^  cm.)  long,  and  passes  more  horizontally 
to  the  root  of  its  lung,  on  a  level  with  the  fourth  thoracic  ver- 
tebra. It  is  larger  in  all  its  diameters  than  the  left ;  hence, 
foreign  bodies  which  have  accidentally  dropped  into  the  trachea 
are  more  likely  to  be  carried  into  the  right  bronchus  by  the  cur- 
rent of  the  air.  The  vena  azygos  major  arches  over  the  right 
bronchus  to  terminate  in  the  superior  vena  cava.     The  left  is 


First  ring  of  trachea. 


Position  of  thyroid  isthmus. 


Fig.  83.  —  Anterior  View  of  the  Larynx,  with  the  Trachea  and  Bronchi. 


about  two  inches  (5  cm)  in  length,  and,  descending  more  ob- 
liquely to  its  lung  than  the  right,  enters  it  on  a  level  with  the  fifth 
thoracic  vertebra.  The  left  bronchus  passes  under  the  arch  of 
the  aorta,  in  front  of  the  oesophagus  and  the  thoracic  duct,  and 
subsequently  crosses  in  front  of  the  descending  aorta. 

The  cartilages  of  the  trachea  vary  in  number  from  sixteen  to 


230  MUCOUS    MEMBRANE. 

twenty,  of  the  right  bronchus  from  six  to  eight,  and  of  the  left 
from  nine  to  tweh^e.  Those  of  the  trachea  form  about  two- 
thirds  of  a  circle,  somewhat  like  a  horseshoe  in  shape,  are  about 
one-sixth  of  an  inch  (/  w;«.)  in  their  vertical  direction,  and  one- 
twenty-fifth  (/  vim)  in  thickness,  and  thicker  in  the  middle  than 
at  the  upper  and  lower  borders.  The  cartilages  are  connected 
and  cov'ered  on  their  outer  and  inner  surfaces  by  a  tough  mem- 
brane, consisting  of  connective  and  elastic  tissues  with  some 
muscular  fibres  {tracheal  nmsclc).  This  membrane  is  attached 
above  to  the  circumference  of  the  cricoid  cartilage,  and  is  con- 
tinued through  the  whole  extent  of  the  trachea  and  bronchial 
tubes.  Posteriorly,  where  the  cartilages  are  deficient,  it  com- 
pletes the  integrity  of  the  air  tube.  In  this  tissue,  which  is  of 
a  pale  reddish  color,  is  a  layer  of  unstriped  muscular  fibres, 
arranged  in  a  transverse  and  a  longitudinal  direction. 

The  first  cartilage  is  the  broadest,  and  is  frequently  divided 
at  one  end  ;  the  last  cartilage  is  placed  at  the  bifurcation  of  the 
trachea,  and  is  shaped  like  the  letter  V ;  its  angle  projects  into 
the  centre  of  the  main  tube,  and  its  sides  belong  one  to  each 
bronchus. 

Muscular  Fibres.  —  This  thin  stratum  of  unstriped  mus- 
cular fibres  consists  of  two  layers,  and  is  brought  into  view 
when  the  fibrous  membrane  and  tracheal  glands  have  been  re- 
moved. The  longitudinal  fibres  are  the  more  external,  and  are 
attached  by  minute  tendons  to  the  extremities  of  the  cartilages  ; 
the  transverse  fibres  {tracJiealis  muscle)  extend  transversely  be- 
tween the  posterior  free  ends  of  the  cartilages.  By  their  con- 
traction they  approximate  the  ends  of  the  cartilages  and  diminish 
the  calibre  of  the  trachea. 

Elastic  Tissue.  —  This  lines  the  whole  tube,  but  is  most 
abundant  at  the  posterior  or  membranous  part  of  the  trachea, 
and  its  fibres  run  in  a  longitudinal  direction.  It  is  this  layer 
which  raises  the  mucous  membrane  into  folds,  and  its  elasticity 
admits  of  the  elongation  and  the  recoil  of  the  tube. 

Tracheal  Glands.  —  Upon  the  outer  surface  of  the  fibrous  layer  of  the  trachea 
are  a  number  of  small  mucous  glands,  most  numerous  on  the  posterior  part  of  the 
tube.  They  are  compound  racemose  glands  lined  with  columnar  epithelium,  and 
their  excretory  ducts  pierce  the  fibrous  and  muscular  layers,  and  terminate  on  the 
free  surface  of  the  mucous  membrane.  In  health  their  secretion  is  clear,  and  just 
sufficient  to  lubricate  the  air-passages.  In  bronchitis  they  are  the  sources  of  the 
abundant  viscid  expectoration. 

Mucous  Membrane.  —  The  mucous  membrane  lining  the  air- 
passages  is  a  continuation  of  that  of  the  larynx.     Its  color  in  the 


MUCOUS    MEMBRANE.  23  I 

natural  state  is  nearly  white,  but  in  catarrhal  affections  it  be- 
comes bright  red  in  consequence  of  the  accumulation  of  blood 
in  the  capillary  vessels.  It  is  continued  into  the  ultimate  air-cells, 
where  it  becomes  thinner  and  more  transparent.  In  its  deeper 
layer  is  found  a  considerable  amount  of    elastic  tissue,  in  its 


Fig.  84. — Anterior  View  OF  THE  Thorax,  WITH  Outlines  of  the  Diaphragm  and  Lungs. 

superficial  layer  a  quantity  of  lymphoid  tissue.  Its  surface  is 
lined  with  a  layer  of  columnar  ciliated  epithelial  cells.  The 
vibratile  movement  of  the  cilia  is  directed  in  such  a  way  as  to 
favor  the  expectoration  of  the  mucus.  The  ciliated  epithelium 
lining  the  mucous  membrane  ceases  at  the  commencement  of 
the  air-cells,  where  it  is  replaced  by  the  squamous  variety. 


232  THE    LUNGS. 

At  the  root  of  the  King  each  bronchus  divides  into  two 
branches,  an  upper  and  a  lower,  corresponding  to  the  lobes  of 
the  lung;  on  the  right  side  the  lower  branch  sends  a  small 
division  to  the  third  lobe  of  the  lung.  The  tubes  diverge 
through  the  lung,  and  divide  into  branches,  successively  smaller 
and  smaller,  until  they  lead  to  the  air-cells.  These  ramifications 
do  not  communicate  with  each  other ;  hence,  when  a  bronchial 
tube  is  obstructed,  all  supply  of  air  is  cut  off  from  those  cells  to 
which  it  leads. 

The  several  tissues  —  cartilaginous,  fibrous,  muscular,  mu- 
cous, and  glandular  —  which  compose  the  air-passages,  are  not 
present  in  equal  proportions  throughout  all  their  ramifications, 
but  each  is  placed  in  greater  or  less  amount  where  it  is  required. 
The  cartilaginous  rings  necessary  to  keep  the  larger  tubes  per- 
manently open  become,  in  the  smaller  tubes,  fewer  and  less 
regular  in  form.  As  the  subdivisions  of  the  tubes  multiply, 
the  cartilages  consist  of  small  pieces  placed  here  and  there  ; 
they  become  less  and  less  firm,  and  finally  disappear  when  the 
tube  is  reduced  to  ^^  of  an  inch  (/  mm.)  in  diameter.  The 
smallest  air-passages  are  entirely  membranous,  being  formed  of 
fibrous,  elastic,  and  muscular  tissues. 

The  Lungs.  —  The  lungs  are  two  in  number,  and  occupy 
the  lateral  cavities  of  the  chest.  Each  is  conical  in  shape,  its 
apex  extending  into  the  neck,  the  base  resting  on  the  upper  or 
convex  surface  of  the  diaphragm.  The  lung  presents  for  ex- 
amination—  an  apex,  a  base,  two  surfaces,  and  two  borders. 

The  apex  extends  upwards  about  an  inch  (^.5  (m.)  above  the 
clavicle,  and  is  generally  marked  by  a  slight  groove  for  the  sub- 
clavian artery.  The  base  is  concave,  and  slopes  downwards  at 
its  posterior  part.  Its  outer  smface,  in  contact  with  the  chest 
wall,  is  smooth  and  convex,  and  is  deeper  behind  than  in  front. 
Its  inner  s?irface  is  concave,  and  hollowed  out  to  accommodate 
the  heart  and  its  large  vessels.  Its  anterior  border  is  sharp, 
and  overlaps  the  large  vessels  and  the  pericardium.  The  pos- 
terior border  is  rounded,  and  rests  in  the  broad  groove  on  the 
side  of  the  bodies  of  the  thoracic  vertebrae.  On  the  inner  con- 
cave surface,  a  little  above  the  middle  and  nearer  the  posterior 
than  the  anterior  border,  is  the  root,  where  the  large  vessels 
and  bronchi  pass  to  and  from  the  lungs. 

Each  lung  is  traversed  on  its  external  surface  by  an  oblique 
fissure  which  pas.ses  deeply  into  its  interior.  It  extends  from 
the  upper  part  of  the  posterior  border,  downwards  and  forwards 


CUNTKACTIBILITV    OF    THE    LUNG.  233 

to  the  anterior  border,  and  on  the  right  side  there  is  a  second 
fissure  passing,  forwards  and  upwards  from  the  obhque  fissure, 
to  the  middle  of  the  anterior  margin.  The  left  lung  presents  a 
deep  notch  in  the  anterior  border  in  which  the  pericardium  is 
seen  as  far  as  the  apex  of  the  heart. 

The  posterior  border  of  the  lung  is  indicated  by  a  line  drawn 
from  the  level  of  the  spinous  process  of  the  seventh  cervical 
vertebra  down  on  either  side  of  the  spine  over  the  costo-verte- 
bral  joints  as  low  as  the  spinous  process  of  the  tenth  thoracic 
vertebra.  The  trachea  bifurcates  opposite  the  fourth  thoracic 
vertebra,  and  from  this  point  the  two  bronchi  are  directed  out- 
ward, the  right  one  almost  horizontally^  the  left  one  with  an 
inclination  downward  and  slightly  forward.  The  lower  border 
of  the  lung  is  marked  with  a  slightly  curved  line,  having  its 
convexity  downward,  drawn  from  the  sixth  costo-chondral 
articulation  to  the  tenth  thoracic  spine.  This  curved  lin^  will 
be  intersected  by  vertical  lines  drawn  from  the  nipple,  from 
the  mid-axilla,  from  the  inferior  scapular  angle  ;  the  first  at  the 
sixth  rib,  the  second  at  the  eighth  rib,  and  the  third  at  the 
tenth  rib.  The  position  of  the  great  fissure  in  the  right  lung 
may  be  indicated  by  a  line  drawn  from  the  second  thoracic 
vertebra  around  the  chest  wall  to  the  sixth  costo-chondral  ar- 
ticulation. The  smaller  or  secondary  fissure  in  the  right  lung 
is  indicated  by  a  line  drawn  from  the  point  where  the  midaxil- 
lary  line  crosses  the  third  or  fourth  rib  downward  and  forward 
to  the  fourth  chondro-sternal  circulation.  —  A.  H. 

Contractibility  of  the  Lung.  —  When  an  openin'r  is  made  into  the  chest,  the 
lung,  which  was  in  contact  with  the  ribs,  immediately  recedes  from  them,  and, 
provided  there  be  no  adhesions,  gradually  contracts.  If  the  lungs  be  artificially 
inflated,  either  in  or  out  of  the  chest,  we  observe  that  they  spontaneously  e.xpel  a 
part  of  the  air.  This  disposition  to  contract,  in  the  living  and  the  dead  lung,  is 
due  to  the  elastic  tissue  in  the  bronchial  tubes  and  the  air-cells ;  but  more  especi- 
ally to  a  layer  of  delicate  elastic  tissue  on  the  surface  of  the  lung,  which  has 
been  described  by  some  anatomi.sts  as  a  distinct  coat,  under  the  name  of  the 
second  or  inner  layer  of  the  pleura.* 

Color.  —  The  lungs  are  of  a  livid  red  or  violet  color ;  they 
often  present  a  mixture  of  tints,  giving  them  a  marble-like  ap- 
pearance. This  is  not  the  natural  color  of  the  organ,  since  it 
is  produced  in  the  act  of  dying.  It  depends  upon  the  stagna- 
tion of  the  venous  blood,  which  the  right  ventricle  still  propels 

*  In  some  animals,  the  seal  especially,  the  elasticity  of  this  tissue  is  very 
strongly  marked. 


234  "^"^    COLOR. 

into  the  lungs,  though  respiration  is  failing.  The  tint  varies  in 
particular  situations  in  proportion  to  the  amount  of  blood,  and 
is  always  deepest  at  the  back  of  the  lung.  But  the  color  of 
the  proper  tissue  of  the  lung,  apart  from  the  blood  which  it 
contains,  is  pale  and  light  gray.  This  color  is  seldom  seen 
except  in  the  lungs  of  infants  who  have  never  breathed,  or 
after  death  from  profuse  haemorrhage. 

Upon  or  near  the  surface  of  the  lungs,  numerous  dark  spots 
are  observed  which  do  not  depend  upon  the  blood,  since  they 
are  seen  in  the  palest  lungs.  They  vary  in  number  and  size, 
and  increase  with  age.  The  source  of  these  discolorations  is 
not  exactly  known  ;  but  they  are  probably  deposits  of  minute 
particles  of  carbonaceous  matter  which  have  been  inhaled  with 
the  air. 

The  lungs  are  composed  of  cartilaginous  and  membranous 
tubes,  of  which  the  successive  subdivisions  convey  the  air  into 
closely-packed  minute  cells,  called  the  air-vesicles  ;  of  the  rami- 
fications of  the  pulmonary  artery  and  veins  ;  of  the  bronchial 
vessels  concerned  in  their  nutrition ;  of  lymphatics  and  nerves. 
These  component  parts  are  united  by  connective  tissue,  and 
covered  externally  by  pleura.  The  part  at  which  they  respec- 
tively pass  in  and  out  is  called  the  root  of  the  lung. 

The  lungs  are  the  lightest  organs  in  the  body,  and  float  in 
water,  their  specific  gravity  varying  from  .345  to  .746.  When 
entirely  deprived  of  air,  they  sink.  This  is  observed  in  certain 
pathological  conditions  ;  e.g.,  when  one  lung  is  compressed  by 
effusion  into  the  chest,  or  rendered  solid  by  inflammation. 

The  surface  of  the  lung  is  closely  invested  by  a  thin,  trans- 
parent layer  of  serous  membrane,  immediately  beneath  which 
is  a  fine  areolar  tissue,  called  subserous,  which  is  very  soft  and 
elastic  so  as  to  allow  of  the  free  expansion  of  the  organ.  This 
tissue  sends  inwards  prolongations,  called  interlobular,  which 
map  out  the  lungs  into  a  number  of  angular  spaces  of  various 
sizes  termed /t'^/z/^j-;  those  on  the  surface,  indicated  by  faint 
white  lines,  are  larger  than  those  in  the  interior  of  the  lung. 
Each  lobule  is  a  lung  in  miniature,  and  consists  of  a  small 
bronchial  tube  and  its  termination  in  dilated  extremities,  called 
infundibula,  of  ramifications  of  the  pulmonary  vessels,  lym- 
phatics, and  nerves,  and,  lastly,  of  the  bronchial  vessels.  The 
cells  of  the  interlobular  tissue  have  no  communication  with  the 
air-vesicles,  unless  the  latter  be  ruptured  by  excessive  straining, 
and  then  this  connective  tissue  becomes  inflated  with  air,  and  is 


MINUTE    STRUCTURE    OF    THE    LUNG. 


235 


called  interlobular  emphysema.     When  infiltrated  with  scrum  it 
constitutes  irdcina  of  the  lung. 

Each  bronchial  tube  divides  and  subdivides  into  smaller  and 
smaller  divergent  tubes,  until  each  has  reached  a  reduced  size 
of  about  -oV  of  an  inch  (/  mm.) ;  it  then  enters  a  pulnionary  lob- 
ule, when  it  is  termed  a  lobular  broncJiial  tube,  and  presents  on 
its  walls  numerous  dilatations,  called  air-cells  or  alveoli,  which 
vary  from  3'^^  to  ^^  of  an  inch  {or  about  \  to  \  mm.)  in  diameter 
(Fig.  85).  Thus  reduced  in  size,  the 
walls  of  the  tubes  no  longer  present 
traces  of  cartilaginous  tissue,  but  are 
composed  of  a  delicate  elastic  mem- 
brane upon  which  the  capillaries  ram- 
ify in  a  very  minute  network.*  Each 
tube  finally  terminates  in  an  enlarged 
irregular  passage  —  alveolar  passage 
—  from  which  proceed  on  all  sides 
numerous  blind  dilatations,  named 
infundibula. 

The  smaller  bronchial  tubes  are 
encircled  by  more  or  less  complete 
rings  of  cartilage ;  but  as  the  tubes 
lessen  in  calibre,  the  rings  become 
less  perfect ;  so  that  when  the  tubes 
are  reduced  to  ^^  of  an  inch  (/  mm)) 
in  diameter,  the  rings  entirely  disappear.  The  continuation  of 
the  air-tubes  consists  simply  of  fibrous  tissue  which  becomes 
gradually  thinner,  so  that  in  the  smallest  tubes  they  are  reduced 
to  simply  membranous  tubes,  and  are  continued  on  as  irregular 
passages  —  intercellular  passages  \  —  which  are  studded  with 
numerous  small  saccules,  termed  air-cells  or  alveoli. 

The  air-cells  are  small,  shallow,  polyhedral  depressions,  y^o  of 
an  inch  (^5  /x)  in  diameter,  separated  by  thin  partitions  or  septa 
which  communicate  freely  with  the  intercellular  passages,  but 
not  with  each  other. 

The  mucous  meinbrajie  which  invests  the  divisions  of  the 
bronchi  as  far  as  the  intercellular  passages  is  lined  with  epithe- 
lium of  the  columnar  ciliated   variety.     At  this  situation  the 

*  In  phthisis  the  expectoration  contains  some  of  the  debris  of  this  elastic  frame- 
work of  the  air-vesicles ;  it  can  be  seen  under  the  microscope,  and  is  a  test  of  the 
character  of  the  sputa. 

tRainey,  I\Ied.  C/iir.   Traits.,  vol.  .xxviii.  1845. 


Fig.  85.  —  Ultimate  Air-cells  of 
THE  Lung  (from  Kolliker). 
Magnified  Twenty-five  Times. 


236  BRONCHIAL    ARTERIES. 

character  of  the  epithelium  changes  to  that  of  a  squamous  kind, 
consisting  of  a  single  layer  of  flat  polygonal  nucleated  cells. 

The  structure  of  the  air-cells  differs  in  some  important  fea- 
tures from  that  of  the  smaller  bronchial  tubes ;  the  muscular 
tissue  disappears,  the  elastic  tissue  is  no  longer  arranged  in 
bundles,  but  becomes  frayed  out  and  intermingled  with  the  con- 
nective tissue. 

Pulmonary  Vessels.  —  The  piUvionary  artery  conveying 
venous  blood  to  the  lungs  divides  and  subdivides  with  the  bron- 
chial tubes,  and  terminates  in  a  fine  dense  capillary  plexus  on 
the  walls  of  the  intercellular  passages  and  air-cells,  beneath  the 
epithelium.  These  plexuses  —  the  pulmonary  capillaries  — 
form  a  single  layer  of  capillaries  which  is  so  close  that  the  inter- 
stices are  even  narrower  than  the  blood-vessels.  The  plexus 
which  ramifies  over  the  air-cell  does  not  communicate  with  the 
plexus  covering  another  air-cell.  The  blood  and  air  are  not  in 
actual  contact.  Nothing,  however,  intervenes  but  the  wall  of 
the  cell  and  the  capillary  vessels,  which  are  such  delicate  struc- 
tures that  they  oppose  no  obstacle  to  the  free  interchange  of 
gases  by  which  the  blood  is  purified.  This  purification  is  ef- 
fected by  the  taking  in  of  oxygen,  and  the  elimination  of  carbonic 
acid  and  watery  vapor.  The  most  complete  purification  takes 
place  in  the  single  layer  of  capillaries  between  the  folds  of  mem- 
brane projecting  into  the  cell ;  for  in  this  situation  both  sides  of 
these  vessels  are  exposed  to  the  action  of  the  air.  The  blood, 
circulating  in  steady  streams  through  this  capillary  plexus,  re- 
turns through  the  pulmonary  veins.  These,  at  first  extremely 
minute,  gradually  coalesce  into  larger  and  larger  branches  which 
anastomose  very  freely,  and  accompany  the  arteries.  They 
finally  emerge  from  the  root  of  the  lung  by  two  large  trunks 
which  carry  the  oxygenated  blood  to  the  left  auricle  of  th-^ 
heart.     The  pulmonary  veins  are  not  provided  with  valves. 

Bronchial  Arteries.  — These  small  arteries,  two  or  more  in 
number,  are  the  nutrient  vessels  of  the  lungs.  The  right  arises 
either  from  the  first  aortic  intercostal,  or,  conjointly  with  the 
left  bronchial,  from  the  thoracic  aorta.  The  left,  usually  two  in 
number,  come  from  the  thoracic  aorta.  They  enter  the  lung 
behind  the  divisions  of  the  bronchi,  which  they  accompany; 
The  bronchial  vessels  are  distributed  in  various  ways  ;  some  of 
their  branches  supply  the  coats  of  the  air-passages,  the  large 
blood-ve-ssels,  and  the  lymphatic  glands  ;  others  the  interlobular 
tissue  ;  a  few  reach  the  surface  of  the  lung  and  ramify  beneath 


THE    PHARYNX.  237 

the  pleura.  The  right  brojicJiial  veins  terminate  in  the  vena 
azygos,  the  left  in  the  superior  intercostal  vein. 

The  nerves  of  the  lung  are  derived  from  the  pneumogastric 
and  the  sympathetic.  They  enter  with  the  bronchial  tubes, 
forming  a  plexus  in  front  and  behind  them,  anterior  and  poste- 
rior pulmonary  plexus,  in  which  are  found  minute  ganglia. 

The  lymphatics  of  the  lungs  consist  of  a  superficial  and  deep 
set  ;  some  commence  in  the  lymphatic  capillaries  in  the  inter- 
lobular tissue,  and  thence  pass  to  the  surface,  forming  a  net- 
work which  communicates  with  the  subpleural  lymphatic  plexus  ; 
others  take  their  origin  in  the  mucous  membrane  of  the  bron- 
chial tubes  ;  and  all  eventually  enter  the  bronchial  glands.  Of 
these  the  larger  are  situated  about  the  bronchi  near  the  root  of 
the  lung,  particularly  under  the  bifurcation  of  the  trachea. 

DISSECTION  OF  THE  PHARYNX. 

Dissection.  —  To  obtain  a  view  of  the  pharynx  cut  through 
the  trachea,  the  oesophagus,  the  large  vessels,  and  nerves  of  the 
neck,  a  short  distance  above  the  first  rib,  and  then  separate 
them  from  the  prevertebral  muscles  which  lie  immediately  in 
front  of  the  bodies  of  the  cervical  vertebras,  and  to  which  they 
are  but  loosely  connected.  Saw  out  a  V-shaped  piece  from  the 
temporal  and  occipital  bones,  the  prongs  of  the  V  pointing  to- 
wards the  anterior  condyloid  foramina.  Introduce  a  fine  jig-saw 
and  aim  for  the  insertion  of  the  rectus  capitis  anticus  muscle  on 
the  basilar  process  of  the  occipital  bone  passing  behind  the  jugu- 
lar foramina.  When  this  is  accomplished  the  student  will  find 
that  the  pharynx  and  larynx  are  left  attached  to  the  anterior 
half  of  the  section,  the  spinal  column  and  the  prevertebral  mus- 
cles to  the  posterior  half.  Tow  should  then  be  introduced 
through  the  mouth  and  oesophagus  to  distend  the  walls  of  the 
pharynx. 

One  side  of  the  pharynx  should  be  dissected  to  show  the  con- 
strictor muscles,  the  other  should  be  reserved  for  the  vessels 
and  nerves  in  immediate  relation  with  the  pharynx. 

General  Description  of  Pharynx. —  The  pharynx  (<f>apvyi, 
the  throat,)  is  the  common  passage  for  the  air  and  the  food. 
Into  it  the  posterior  nares  (2)  (choanae),  the  isthmus  of  the  fau- 
ces from  the  mouth,  eustachian  tubes  (2),  larynx,  and  oesopha- 
gus open.  It  is  a  funnel-shaped  muscular  bag,  about  four  and 
a  half   inches  {ll.J  cm)  in  length,  and  broader  in  its  transverse 


238  THE    PHARYNX, 

than  in  its  anteroposterior  diameter.  Its  broadest  portion  is 
situated  opposite  the  os  hyoides,  and  it  then  gradually  tapers  as 
far  as  the  cricoid  cartilage,  where  it  is  continuous  with  the 
oesophagus,  which  is  its  narrowest  portion.  Its  nppcr  part  is 
attached  to  the  basilar  process  of  the  occipital  bone  and  the 
petrous  portions  of  the  temporal  bones;  behmd,  it  is  loosely 
connected  by  deep  cervical  fascia  with  the  prevertebral  mus- 
cles ;  *  in  front,  it  is  attached  to  the  internal  pterygoid  plates 
and  hamular  processes  of  the  sphenoid,  to  the  pterygo-mandibu- 
lar  ligaments,  the  mandible,  the  tongue,  the  hyoid  bone,  and 
the  stylo-hyoid  ligaments,  and  to  the  thyroid  and  cricoid  carti- 
lages ;  laterally,  it  is  loosely  connected  to  the  styloid  muscles, 
and  it  has  in  close  relation  with  it  the  common  and  internal 
carotid  arteries,  the  glosso-pharyngeal,  pneumogastric,  spinal 
accessory,  hypoglossal,  and  sympathetic  nerves  ;  the  internal 
pterygoid,  tensor  palati,  and  stylo-pharyngeus  muscles  ;  the  lin- 
gual and  ascending  pharyngeal  arteries,  the  superior  laryngeal 
and  external  laryngeal  nerves,  the  ascending  palatine  artery, 
and  the  internal  jugular  vein.  Its  dimensions  are  not  equal 
throughout.  Its  breadth  at  the  upper  part  is  equal  to  that  of 
the  posterior  openings  of  the  nose  {choana:)  ;  here  it  is  only  re- 
quired to  conyey  air,  but  it  becomes  much  wider  in  the  situation 
where  it  transmits  the  food  —  that  is,  at  the  back  of  the  mouth; 
thence  it  gradually  contracts  to  the  oesophagus.  The  pharynx, 
therefore,  may  be  compared  to  a  funnel  communicating  in  front 
by  wide  apertures  with  the  nose,  the  mouth,  and  the  larynx  ; 
while  the  oesophagus  represents  the  tube  leading  from  its  lower 
end.  The  upper  part  of  the  funnel  forms  a  cul-de-sac  at  the 
basilar  process  of  the  occipital  bone.  At  this  part  there  is,  on 
each  side,  the  opening  of  a  narrow  canal,  called  the  Eustachian 
tube,  through  which  air  passes  to  the  tympanum  of  the  ear.f 
Before  the  muscles  of  the  pharynx  can  be  examined,  we  must 

*  It  is  in  this  tissue  (which  never  contains  fat)  that  post- pharyngeal  abscesses 

are  seated. 

t  Observe  that  the  pharynx  conducts  to  the  oesophagus  by  a  gradual  contrac- 
tion of  its  channel.  This  transition,  however,  is  in  some  cases  sufficiently  abrupt 
to  detain  a  foreign  body,  such  as  a  morsel  of  food  more  l)ulky  than  usual,  at  the 
top  of  the  ccsophagus.  If  such  a  substance  become  firmly  impacted  in  this  situa- 
tion, one  can  readily  understand  that  it  will  not  only  prevent  the  descent  of  food 
into  the  stomach,  but  that  it  may  occasion,  by  its  pressure  on  the  trachea,  alarming 
sv-mptoms  of  suffocation.  Supposing  that  the  obstacle  can  neither  be  removed 
by  the  forceps,  nor  pushed  into  the  stomach  by  the  probang,  it  may  then  become 
necessary  to  extract  it  by  making  an  incision  into  the  ccsophagus  on  the  Itft  side 
of  the  neck. 


CONSTRICTOR    MUSCLES    OF    THE    PHARYNX. 


239 


remove  a  layer  of  thin  fascia,  termed  the  pharyngeal  fascia.  It 
is  the  layer  of  deep  cervical  fascia  behind  the  pharynx,  and 
must  not  be  confounded  with  the  ^^xo^ox  pharytigcal  aponeurosis, 
which  intervenes  between  its  muscular  and  mucous  walls. 

At  the  back  of  the  pharynx,  near  the  base  of  the  skull,  are  a 
few  lynipJiatic  glands.  They  sometimes  enlarge,  and  form  a 
perceptible  tumor  in  the  pharynx. 


Obicularis  oris, 

Pterygo-mandibular  ) 
ligament.  | 


Mylo-hyoideus. 

Os  hyoides. 

Thyro-hyoid  ligament. 

Pomum  AdamL 


Cricoid  cartilage 
Trachea 


Glosso-pharyngeal  n. 
Stylo-pharyngeus. 


Superior  laryngeal 
n.  and  a. 


External  laryngeal  n. 
Crico-thyroideus. 

Inferior  laryngeal  n. 
CEsophagus. 


Fig.  86.  —  Side  View  of  the  Muscles  of  the  Pharynx. 


In  removing  the  fascia  from  the  pharyngeal  muscles,  notice 
that  a  number  of  veins  ramify  and  communicate  in  all  directions. 
They  constitute  the  pharyngeal  venous  plexus,  and  terminate 
in  the  internal  jugular  vein. 

Constrictor  Muscles  of  the  Pharynx.  — They  are  three  in 


240  CONSTRICTOR    MUSCLES    OF    THE    PHARYNX. 

number  and  arranged  so  that  they  overlap  each  other,  i.e.,  the 
inferior  overlaps  the  middle,  and  the  middle  the  superior  (Fig. 
86).  They  have  the  same  attachments  on  both  sides  of  the 
body  ;  and  the  fibres  from  the  right  and  left  meet  together  and 
are  inserted  in  the  mesial  line,  the  insertion  being  marked  by  a 
white  longitudinal  line,  called  the  rapJi^. 

The  inferior  constrictor,  the  most  superficial  and  thickest  of 
the  thin  constrictors,  arises  from  the  side  of  the  cricoid  cartilage 
behind  the  crico-thyroid  muscle,  from  the  surface  behind  the 
oblique  ridge  and  the  lower  cornu  of  the  thyroid  cartilage.  Its 
fibres  expand  over  the  lower  part  of  the  pharynx.  The  superior 
fibres  ascend  ;  the  middle  run  transversely ;  the  inferior  de- 
scend slightly,  and  are  inserted  into  the  posterior  median  raphe. 
The  lower  fibres  are  continuous  with  those  of  the  oesophagus. 
Beneath  its  lower  border  the  recurrent  laryngeal  nerve  enters 
the  larynx.  Its  noi^e-supply  is  from  the  pharyngeal  plexus,  the 
external  laryngeal,  and  the  recurrent  laryngeal  nerves. 

In  order  to  completely  expose  the  next  muscle,  the  right  half 
of  the  interior  constrictor  should  be  reflected  from  the  middle 
line. 

The  middle  constrictor  arises  from  the  upper  edge  of  the 
greater  cornu  of  the  os  hyoides,  from  its  lesser  cornu,  and  part 
of  the  stylohyoid  ligament,  and  is  inserted  into  the  posterior 
median  raphe.  Its  fibres  take  different  directions,  so  that,  with 
those  of  the  opposite  muscle,  they  form  a  lozenge.  The  lower 
angle  of  the  lozenge  is  covered  by  the  inferior  constrictor ;  the 
upper  angle  ascends  nearly  to  the  basilar  process  of  the  occipi- 
tal bone,  and  terminates  upon  the  pharyngeal  aponeurosis.  The 
external  surface  of  the  muscle  is  covered  at  its  origin  by  the 
hyo-glossus,  from  which  it  is  separated  by  the  lingual  artery ; 
while  beneath  it  are  the  superior  constrictor,  the  stylo-pharyn- 
geus,  and  palato-pharyngeus  muscles  and  the  pharyngeal  apon- 
eurosis.     Its  nerve  comes  from  the  pharyngeal  plexus. 

Between  the  middle  and  inferior  constrictors,  the  superior 
laryngeal  artery  and  nerve  perforate  the  thyro-hyoid  membrane 
to  supply  the  larynx. 

The  superior  constrictor  consists  of  pale  muscular  fibres,  and 
arises  from  the  hamular  process  of  the  sphenoid  bone,  and  from 
the  lower  part  of  its  internal  pterygoid  plate  ;  from  the  tuber- 
osity of  the  palate  bone  and  the  reflected  tendon  of  the  tensor 
palati  ;  from  the  pterygo-mandibular  ligament  (which  connects 
it   with   the    buccinator)  ;    from   the   back   part   of    the  myloid 


CONSTRICTOR    MUSCLES    OF    THE    TIIARYNX. 


241 


ridge  of  the  mandible,  and  from  the  side  of  the  tongue.  The 
fibres  pass  backwards  to  the  mesial  raphe  ;  some  of  them  are 
inserted  through  the  medium  of  the  pharyngeal  aponeurosis  into 
the  basilar  process.  Its  nerve  comes  from  the  pharyngeal 
plexus. 

The  upper  border  of  the   superior  constrictor  presents,    on 
either  side,  a  free  semilunar  edge  with  its  concavity  upwards,  so 


Fig.  87.  —  View  of  thl  Constrictor  Muscles  prom  Behind. 


that,  between  it  and  the  base  of  the  skull,  a  space  is  left  in 
which  the  muscle  is  deficient  (Fig.  87).  Here  the  pharynx  is 
strengthened  and  walled  in  by  its  own  aponeurosis.  The  space 
is  called  the  simis  of  Morgagni ;  and  in  it,  with  a  little  dissec- 
tion, we  expose  the  muscles  which  raise  and  tighten  the  soft 
palate,  i.e.,  the  levator  palati  and  the  tensor  palati.  The  Eusta- 
chian tube  opens  into  the  pharynx  just  here.     The  fibres  of  the 


242  OPENINGS  INTO  THE  PHARYNX. 

stylo-pharyngeus  pass  in  between  the  superior  and  middle  con- 
strictors, and  expand  upon  the  side  of  the  pharynx  ;  some  of 
them  mingle  with  those  of  the  constrictors,  so  as  to  be  able  to 
lift  up  the  pharynx  in  deglutition  ;  but  most  of  them  are  inserted 
into  the  superior  and  posterior  margins  of  the  thyroid  cartilage. 

Action  of  Pharyngeal  Muscles.  —  The  pharyngeal  spine 
of  the  occipital  bone  being  the  fixed  point,  the  muscles  contract 
from  above  downward  through  the  median  raphe.  The  larynx 
being  raised,  and  the  tongue  pressing  upon  the  soft  palate  in 
its  projection  backwards,  force  the  food  into  the  embrace  of 
the  superior  constrictor  after  it  has  passed  the  isthmus.  As  the 
superior  constrictor  arises  on  a  higher  plane  than  that  of  the 
food  projected  into  it,  there  is  exerted  upon  the  bolus  by  this 
muscle  pressure  on  three  sides,  as  well  as  from  above  down- 
wards. The  middle  and  inferior  constrictors  exert  lateral  pres- 
sure upon  the  bolus  of  food.  May  not  these  muscles  combined 
act  as  a  sounding-board  in  the  expression  of  sound  ?  —  A.  H. 

Pharyngeal  Aponeurosis.  —  The  pJiaryngeal  aponeurosis 
intervenes  between  the  muscles  and  the  mucous  membrane  of 
the  pharynx.  It  is  attached  to  the  basilar  process  of  the  occipi- 
tal bone,  and  to  the  points  of  the  petrous  portions  of  the  tem- 
poral bones.  It  maintains  the  strength  and  integrity  of  the 
pharynx  at  its  upper  part,  where  the  muscular  fibres  are  defi- 
cient ;  but  it  gradually  diminishes  in  thickness  as  it  descends, 
and  is  finally  lost  on  the  oesophagus.  Notice  the  number  of 
mucous  glands  upon  this  aponeurosis,  especially  near  the  base 
of  the  skull  and  the  Eustachian  tube.  These  glands  sometimes 
enlarge  and  cause  deafness  from  the  pressure  on  the  tube. 

Openings  into  the  Pharnyx.  —  Lay  open  the  pharynx  by  a 
longitudinal  incision  in  the  middle  line,  up  to  the  pharyngeal 
tubercle;  then  divide  transversly,  for  a  short  distance,  that  part 
of  the  pharyngeal  aponeurosis  which  is  attached  to  the  basilar 
process,  so  as  the  better  to  view  the  cavity  of  the  pharynx. 
Observe  the  seven  openings  leading  into  it  (Fig.  88)  :  i.  The 
two  posterior  nares  {choanae) ;  below  the  nares  is  the  soft  palate, 
with  the  uvula.  2.  On  either  side  of  them,  near  the  lower  tur- 
binated bones,  are  the  openings  of  the  Eustachian  tubes.  3. 
Below  the  soft  palate  is  the  communication  with  the  mouth, 
called  the  isthmus  faucium.  On  either  side  of  this  are  two  folds 
of  mucous  membrane,  constituting  the  anterior  and  posterior 
half-arches  of  the  palate  ;  between  them  arc  the  tonsils.  Below 
the  isthmus  faucium  is  the  epiglottis,  which  is  connected  to  the 


ISTHMUS     1-AUCIUM.  243 

base  of  the  tongue  by  three  folds  of  mucous  membrane.  4.  Be- 
low the  epiglottis  is  the  aperture  of  the  larynx.  5.  Lastly,  is 
the  opening  into  the  oesophagus.* 

The  pharynx  consists  of  three  coats,  viz.,  muscular,  fibrous, 
and  mucous.     The  two  former  have  been  already  described. 

Mucous  Membrane.  —  The  mucous  membrane  is  common  to 
the  entire  tract  of  the  respiratory  passages  and  the  alimentary 
canal.  This  membrane,  however,  presents  varieties  in  the  dif- 
ferent parts  of  these  channels,  according  as  they  are  intended 
as  passages  for  air  or  for  food.  The  mucous  membrane  of  the 
pharynx  above  the  velum  palati,  being  intended  to  transmit  air 
only,  is  very  delicate  in  its  texture,  and  lined  by  columnar  cil- 
iated epithelium  like  the  rest  of  the  air-passages.  But  opposite 
the  fauces,  the  mucous  membrane  resembles  that  of  the  mouth, 
and  is  provided  with  squamous  epithelium.  At  the  back  of  the 
larynx  the  membrane  is  corrugated  into  folds,  to  allow  the  ex- 
pansion of  the  pharynx  during  the  passage  of  the  food. 

The  membrane  is  lubricated  by  a  secretion  from  the  numerous 
mucous  glands  which  are  situated  in  the  submucous  tissue 
throughout  the  whole  extent  of  the  pharynx,  particularly  in  the 
neighborhod  of  the  Eustachian  tubes. f 

Posterior  Openings  of  the  Nasal  Fossae.  —  These  are  two 
oval  openings,  each  of  which  is  about  an  inch  {2.^  cm)  in  the 
long,  and  half  an  inch  (/J  mm.)  in  the  short  diameter.  They 
are  bounded  above  by  the  body  of  the  sphenoid  bone,  exter- 
nally by  its  pterygoid  plate,  below  by  the  horizontal  portion  of 
the  palate  bone  ;  they  are  separated  from  each  other  by  the 
vomer. 

On  removing  the  mucous  membrane  from  the  posterior  part 
of  the  roof  of  the  nose  and  the  top  of  the  pharynx,  you  will  find 
beneath  it  much  fibrous  tissue.  Hence  polypi  growing  from 
these  parts  are,  generally,  of  a  fibrous  nature. 

Isthmus  Faucium.  —  This  name  is  given  to  the  opening  by 
which  the  mouth  communicates  with  the  pharynx.  It  is  bounded 
above  by  the  soft  palate  and  uvula,  below  by  the  root  of  the 
tongue,  and  on  either  side  by  the  arches  of  the  palate,  enclosing 
the  tonsils  between  them. 

*  On  reflecting  the  mucous  membrane  at  the  pharyngeal  termination  of  the 
Eustachian  tube,  a  thin  pale  muscle,  the  salpiiigo-pharyngeus,  can  be  made  out. 
It  arises  by  a  thin  tendon  from  the  Eustachian  tube,  and  joins  the  palatopharyn- 
geus.      It  is  lost  among  the  fibres  of  the  constrictor  muscles. 

t  This  aggregation  of  mucous  glands  is  called  the  pharyngeal  tonsil. 


244 


THE    SOFT    PALATE. 


Soft  Palate,  or  Velum  Pendulum  Palati.  —  This  movable 
prolongation  of  the  roof  of  the  mouth  is  attached  to  the  border 
of  the  hard  palate,  and  laterally  to  the  side  of  the  pharynx  an- 
teriorly to  posterior  margin  of  the  palate  process  of  the  palatine 
bone.     Posteriorly  it  has  a  free  edge,  with  a  pendulous  conical 


\\   \\\i  I  arch. 


~  Eustachian  tube. 
Levator  palaii  ni. 


f Tensor  palati  m. 

Hamular  process. 


Posterior  palatine 

arch. 
Tonsil. 


Anterior  palatine 
arch. 

Epiglottis. 

Aryteno  epiglot- 
tidean  fold. 

Opening  into  the 
larynx. 


Opening  into  the 
oesophagus. 


Fig.  88.  — Diagrammatic  View  of  the  Pharynx  laid  open  from  behind. 

projection  in  the  centre,  called  the  7ivii/a.  It  constitutes  an 
imperfect  partition  between  the  mouth  and  the  posterior  nares 
{clioance).  Its  upper  or  nasal  surface  is  convex,  and  continuous 
with  the  floor  of  the  nose,  its  lower  surface  is  concave,  in  adap- 
tation to  the  back  of  the  tongue,  and  is  marked  in  the  middle  by 
a  ridge  or  raph^,  indicating  its  original  formation  by  two  lateral 


ARCHES    OR    PILLARS    OF    THE    PALATE.  245 

halves.  The  soft  palate,  when  at  rest,  hangs  obliquely  down- 
wards and  backwards  ;  but  in  swallowing,  it  is  raised  to  the 
horizontal  position  by  the  levatores  palati,  and  is  pushed  up  by 
the  bolus  of  food  and  tongue,  comes  into  apposition  with  the 
back  of  the  pharynx,  and  thus  prevents  the  food  from  passing 
through  the  nose. 

On  making  a  perpendicular  section  through  the  soft  palate, 
you  come  first  upon  the  oral  mucous  membrane  ;  then  you  see 
that  the  great  bulk  of  it  is  made  up  of  muciparous  glands,  which 
lie  thick  on  its  under  surface  to  lubricate  the  passage  of  the 
food.  Above  these  glands  is  the  thin  layer  of  the  palato-glossus, 
then  the  insertion  of  the  tensor  palati  forming  the  broad  apon- 
eurosis of  the  palate ;  still  higher,  are  the  two  portions  of  the 
palato-pharyngeus,  separated  by  the  fibres  of  the  levator  palati, 
the  azygos  uvulae,  and,  lastly,  the  nasal  mucous  membrane. 
The  soft  palate  is  supplied  with  blood  by  the  descending  pala- 
tine branch  of  the  internal  maxillary,  the  ascending  palatine 
branch  of  the  facial,  the  ascending  pharyngeal  and  the  dorsales 
linguce  of  the  lingual  artery.  Its  nerves  are  derived  from  the 
palatine  branches  of  the  maxillary  division  of  the  fifth  and  from 
the  glosso-pharyngeal. 

Uvula.  —  The  uvula  projects  from  the  middle  of  the  soft 
palate,  and  gives  the  free  edge  of  it  the  appearance  of  a  double 
arch.  It  contains  a  number  of  muciparous  glands,  and  a  small 
muscle,  the  azygos  uviileB  which  is  double  and  not  single  as  the 
name  implies.  Its  length  varies  according  to  the  state  of  its 
muscle.  It  occasionally  becomes  permanently  elongated,  and 
causes  considerable  irritation,  a  tickle  in  the  throat,  and  harass- 
ing cough.  When  you  have  to  remove  a  portion  of  it,  cut  off 
only  the  redundant  mucous  membrane. 

Arches  or  Pillars  of  the  Palate.  —  The  soft  palate  is  con- 
nected with  the  tongue  and  pharynx  by  two  folds  of  mucous 
membrane  on  each  side,  enclosing  muscular  fibres.  These  are 
the  anterior  2Ci\^  posterior  arches  or  pillars  of  the  palate.  The 
anterior  arcJi  describes  a  curve  downwards  and  forwards,  from 
the  base  of  the  uvula  to  the  side  of  the  tongue.  It  is  well  seen 
when  the  tongue  is  extruded.  The  posterior  arch,  commencing 
at  the  side  of  the  uvula,  curves  downwards  and  backwards,  along 
the  free  margin  of  the  palate,  and  terminates  on  the  side  of  the 
pharynx.  The  posterior  arches,  when  the  tongue  is  depressed, 
can  be  seen  through  the  span  of  the  anterior.  The  pillars  of 
each  side  diverge  from  their  origin,  and  in  the  triangular  space 


246  CIRCUMFLEXUS    OR    TENSOR    PALATI. 

thus  formed  is  situated  the  tonsil.  The  chief  use  of  the  arches 
of  the  palate  is  to  assist  in  deglutition.  The  anterior,  enclosing 
the  palato-glossi  muscles,  contract  so  as  to  prevent  the  food 
from  coming  back  into  the  mouth  ;  the  posterior,  enclosing  the 
palato-phaiyngci,  contract  like  side  curtains,  and  co-operate  in 
preventing  the  food  from  passing  into  the  nose.  In  vomiting, 
food  does  sometimes  escape  through  the  nostrils,  but  one  cannot 
wonder  at  this,  considering  the  violence  with  which  it  is  driven 
into  the  pharynx. 

Muscles  of  the  Soft  Palate.  —  The  muscles  of  the  soft 
palate  lie  immediately  beneath  the  mucous  membrane.  There 
are  five  pairs  —  namely,  the  levatores  palati,  the  circumflexi  or 
tensores  palati,  the  palato-glossi,  the  palato-pharyngei,  and  the 
azygos  uvulse.  This  last  pair  is  sometimes  described  as  a 
single  muscle.  To  clean  the  muscles,  the  soft  palate  should  be 
made  tense  by  means  of  hooks,  as  they  are  severally  dissected. 

Levator  Palati.  —  This  muscle  arises  ixoxsx  the  under  aspect 
of  the  apex  of  the  petrous  portion  of  the  temporal  bone,  and 
from  the  under  part  of  the  cartilage  of  the  Eustachian  tube.  It 
descends  obliquely  inwards,  and  then  passes  over  the  concave 
border  of  the  superior  constrictor  into  the  pharynx,  where  its 
fibres  spread  out  and  are  inserted  ^Xov^g  the  upper  surface  of  the 
soft  palate  below  the  azygos  uvulae,  meeting  those  of  its  fellow 
in  the  middle  Hne  (Fig.  89).  Its  action  is  to  raise  the  soft 
palate,  so  as  to  make  it  horizontal  in  deglutition  and  in  speaking 
preventing  the  nasal  twang.  It  is  supplied  by  the  descending 
palatine  branch  from  the  spheno-palatine  ganglion. 

Circumflexus  or  Tensor  Palati.  —  This  muscle  is  situated 
between  the  internal  pterygoid  m.  and  the  internal  pterygoid 
plate  of  the  sphenoid  bone.  It  arises  by  a  flattened  muscular 
belly  from  the  scaphoid  fossa,  and  from  the  spine  of  the  sphenoid; 
from  the  outer  surface  and  anterior  margin  of  the  cartilage  of  the 
Eustachian  tube.  Thence  it  descends  perpendicularly,  and  ends 
in  a  tendon  which  winds  round  the  hamular  process,  where  there 
is  a  synovial  bursa.  Now  changing  its  direction,  the  tendon 
passes  horizontally  inwards,  and  expands  into  a  broad  aponeu- 
rosis, which  is  inserted  into  the  horizontal  plate  of  the  palate 
bone,  and  is  also  connected  to  its  fellow  of  the  opposite  side. 
It  gives  strength  to  the  soft  palate.  A  synovial  membrane 
facilitates  the  play  of  the  tendon  round  the  hamular  process. 
Its  action  is  to  draw  down  and  tighten  the  soft  palate,  and, 
owing  to  its  insertion  into  the  palate  bone,  also  to  keep  the 


AZYGOS  OR  LEVATOR  UVVLJE. 


247 


Fig.   8g.  —  Pharynx   Open    Posteriorly,   Showing   Larynx,   Tongue,    and   Soft   Palate. 

A.  Cartilaginous  expansion  of  the  Eustachian  tube.  B.  Posterior  nasal  openings.  C.  .Soft  palate. 
I).  Uvula.  E.  Posterior  pillar  of  tlie  palate.  F.  Tonsil.  G,  G.  Pliaiyiix  opened  in  median 
line.  H.  Base  of  the  tongue.  I.  Epiglottis.  K.  Left  glosso-epiglottidean  fold.  L.  .Superior 
opening  of  the  larynx.  I\I.  Thyroid  cartilage.  N.  Posterior  surface  of  the  larynx.  O.  Group 
of  grape-like  glands  constantly  found  in  these  positions.  P.  Upper  extremity  of  the  oesophagus. 
I.  Azy^os  uvuloT  muscle.  2.  Levator  palati  muscle.  3,  3.  Palato-pharyngeus  mu?cle. 
4.  Salpmgo-pharyngeus  muscle.  5.  Internal  portion  of  the  palato-pharyngeus  muscle.  6.  Fibres 
proceeding  from  the  middle  of  the  palate  and  ending  in  the  palato-pharyngeus  muscle.  7.  Supe- 
rior fibres  of  tlie  palato-pharyngeus  muscle  going  to  interlace  on  the  lateral  and  posterior  sur- 
face of  the  pharynx  with  those  of  the  opposite  side.  8.  Inferior  fibres  of  the  palato-pharyngeus 
muscle  being  inserted  into  the  posterior  margin  of  the  thyroid  cartilage  near  the  base  of  the 
superior  cornu  and  pharyngeal  aponeurosis.  9.  Anterior  fibres  of  the  stylo-pharyngeus  muscle 
attached,  ist,  to  the  lateral  fold  of  the  epiglottis  ;  2d,  to  the  superior  cornu  of  the  thyroid  cartilage 
at  the  base  and  superior  margin.     10.   Superior  constrictor  of  the  pharynx. 


Eustachian   tube   open.       Its   nerve   is   derived  from   the  otic 
ganglion,  and  enters  the  muscle  on  its  inner  aspect. 

Azygos   or   Levator   Uvulae.  —  This   consists   of    two  thin 
bundles  of  parallel  muscular  fibres  situated  one  on  each  side  of 


248  THE    TONSILS. 

the  middle  line.  It  arises  from  the  aponeurosis  of  the  palate 
and  descends  along  the  uvula  nearly  down  to  its  extremity.  It 
receives  its  nerve  from  the  descending  palatine  branch  of  the 
spheno-palatine  ganglion. 

Palato-glossus  and  Palato-pharyngeus.  —  These  muscles 
are  contained  within  the  arches  of  the  soft  palate,  and  the  mu- 
cous membrane  must  be  removed  in  order  to  expose  them.  The 
palato-glossusy  within  the  anterior  arch,  proceeds  from  the  in- 
terior surface  of  the  soft  palate  to  the  side  of  the  tongue,  and  is 
lost  in  the  stylo-glossus  muscle.  T\\q  palato-pliaryiigeus,  within 
the  posterior  arch,  arises  from  the  posterior  border  of  the  soft 
palate  by  two  origins,  separated  by  the  levator  palati.  As  it 
descends  its  fibres  spread  out,  and,  passing  along  the  side  of  the 
pharynx,  blend  with  the  fibres  of  the  inferior  constrictor  and 
the  stylo-pharyngeus.  The  action  of  the  palato-glossus  is  to 
draw  down  the  palate  when  the  pharynx  is  fixed  ;  the  palato- 
glossus to  elevate  the  sides  of  the  tongue  when  the  soft  palate  is 
fixed  ;  both  motions  combined  close  this  portion  of  the  fauces, 
as  is  necessary  in  swallowing.  Their  separate  action  is  called 
into  play  in  speaking.  The  action  of  the  palato-pharyngeus  is 
to  draw  together  the  posterior  pillars  ;  to  depress  the  palate 
when  the  pharynx  is  fixed ;  to  elevate  the  pharynx  when  the 
palate  is  fixed.  Both  these  muscles  are  supplied  by  the  de- 
scending palatine  branches  of  the  spheno-palatine  ganglion. 

Tonsils.  —  The  tonsils  are  two  glandular  bodies  \  of  an  inch 
(/J  mm.)  long,  I  of  an  inch  (8  mm.)  in  width  and  thickness,  sit- 
uated at  the  entrance  of  the  fauces,  between  the  arches  of  the 
soft  palate.  They  are  rounded  in  shape,  and  their  use  is  to  lubri- 
cate the  fauces  during  the  passage  of  the  food.  On  their  inner 
surface  are  visible  from  twelve  to  fifteen  orifices  leading  into 
crypts,  which  make  the  tonsil  appear  like  the  shell  of  an  almond. 
Hence,  as  well  as  from  their  oval  figure,  they  are  called  the 
amygdalcE.     (Fig.  90.) 

These  openings  lead  into  small  follicles  in  the  substance  of 
the  tonsil,  lined  by  a  mucous  membrane.  Their  walls  are  thick, 
and  around  them  is  a  layer  of  closed  cells  (like  Peyer's  glands) 
situated  in  the  submucous  tissue.  The  fluid  secreted  by  these 
cells  is  viscid  and  transparent,  in  the  healthy  state  ;  but  it  is  apt 
to  become  white  and  opaque  in  inflammatory  affections  of  the 
tonsils,  and  occasionally  accumulates  in  these  superficial  de- 
pressions, giving  rise  to  the  deceptive  appearance  of  a  small 
ulcer,  or  a  slough,  or  even  a  false  membrane  on  the  part. 


THE    TONSILS. 


249 


The  tonsil  lies  close  to  the  inner  side  of  the  internal  carotid 
artery.  It  is  only  separated  from  this  vessel  by  the  ascending 
pharyngeal  artery,  the  superior  constrictor,  and  the  aponeurosis 
of  the  pharynx.  Therefore,  in  removing  a  portion  of  the  tonsil, 
or  in  opening  an  abscess  near  it,  the  point  of  the  instrument 
should  never  be  directed  outwards,  but  inivards  towards  the 
mesial  line.*  The  tonsil  is  supplied  with  blood  by  the  tonsillar 
and  palatine  branches  of  the  facial,  and  by  the  descending  pala- 


FiG.  go. — Vertical  Section  of  the  Nasal  Foss.e  and  Mouth. 

Left  nares.  2.  Lateral  cartilage  of  tlie  nose.  3.  Portion  of  the  internal  alar  cartilage  forming 
the  skeleton  of  the  lower  part.  4.  Superior  meatus.  5.  Middle  meatus.  6.  Inferior  meatus. 
7.  Sphenoidal  sinuses.  S  F^xternal  boundary  of  the  posterior  nares.  q.  Internal  elliptical 
opening  of  the  Eustachian  tube.  10.  Soft  palate.  11.  Vestibule  of  the  mouth.  12.  Vault  of 
palate.  13.  tlenio-glossus  muscle.  14.  Genio-hyoid  muscle.  15.  Cut  margin  of  the  mylo- 
hyoid muscle.  16.  Anterior  pillar  of  the  palate  (ant.  half-arch),  presenting  a  triangular  figure 
with  the  base  inferiorly,  covering  partly  the  tonsil.  17.  Posterior  pillar  (post,  half-arch)  of  the 
palate.  18.  Tonsil.  19.  F"ollicular  (mucous)  glands  at  the  base  of  the  tongue.  20.  Cavity  of 
the  larynx.  21.  Ventricle  of  the  larynx.  22.  Kpiglottis.  23.  Cut  os  hyoides.  24.  Cut  thy- 
roid cartilage.  25.  Thyro-hyoid  membrane.  26.  .Section  of  posterior  portion  of  the  cricoid 
cartilage.  27.  Section  of  the  anterior  portion  of  the  same  cartilage.  28.  Crico-thyroid  mem- 
brane. 


*  Ca.ses  are  related  by  Portal  and  Beclard.  in  which  the  carotid  artery  was 
punctured  in  opening  an  abscess  in  the  tonsil.  The  result  was  immediately  fatal 
hemorrhage.  It  should,  however,  be  borne  in  mind  that  the  artery  usually  injured 
is  the  tonsillar  branch  of  the  facial  artery,  and  not  the  internal  carotid.  The  sur- 
gical treatment  of  this  accident  is  therefore  ligature  of  the  external  carotid  artery 
between  its  superior  thyroid  and  lingual  branches,  and  not  ligature  of  the  common 
carotid  artery,  as  is  often  recommended. 


250 


HARD    PALATE. 


tine  branch  of  the  internal  maxillary.  Nerves  are  furnished  to 
it  from  the  glosso-pharyngeal  and  from  Meckel's  ganglion. 

Eustachian  Tube.  —  This  canal  conveys  air  from  the  phar- 
ynx to  the  tympanum.  Its  orifice  is  situated  opposite  the  back 
part  of  the  inferior  turbinated  bone.  The  direction  of  the  tube 
from  the  pharynx  is  upwards,  backwards,  and  outwards  ;  it  is 
an  inch  and  a  half  ( J.cS*  cm)  long.  The  narrowest  part  is  about 
the  middle,  and  here  its  walls  are  in  contact.  Near  the  tympa- 
num its  walls  are  osseous,  but  towards  the  pharynx  they  are 
composed  of  fibro-cartilage  and  fibrous  membrane.  The  carti- 
laginous end,  about  an  inch  {2.^  cm)  in  length,  projects  between 
the  origins  of  the  levator  and  the  tensor  palati,  and  gives  attach- 
ment to  some  of  their  fibres,  and  also  some  of  the  palato-phar- 
yngeus,  now  called  the  salpingo-pharyngeus.  It  is  situated  at 
the  base  of  the  skull,  in  the  furrow  between  the  petrous  portion 
of  the  temporal  and  the  great  wing  of  the  sphenoid  bone.  It 
adheres  closely  to  the  bony  furrow,  as  well  as  to  the  fibro-car- 
tilage filling  up  the  foramen  lacerum  medium.  The  orifice  is 
not  trumpet-shaped,  as  usually  described,  but  an  elliptical  slit 
about  half  an  inch  (/J  mm)  long,  and  nearly  perpendicular. 
The  fibro-cartilage  bounds  it  only  on  the  inner  and  upper  part 
of  the  circumference  ;  the  integrity  of  the  canal  below  is  main- 
tained by  tough  fibrous  membrane. 

The  Eustachian  tube  is  lined  by  a  continuation  of  the  mucous 
membrane  of  the  pharynx,  and  covered  by  ciliated  epithelium. 
That  which  lines  the  cartilaginous  portion  of  the  tube  is  thick 
and  vascular,  and  gradually  becomes  thinner  towards  the  tym- 
panum. Hence,  inflammatory  affections  of  the  throat  or  tonsils 
are  liable  to  be  attended  with  deafness,  from  temporary  obstruc- 
tion of  the  tube. 

Mucous  glands  surround  the  orifice  of  the  tube,  and  are  sim- 
ilar in  nature  and  function  to  the  glands  beneath  the  mucous 
membrane  of  the  mouth,  the  palate,  and  the  pharynx. 

Hard  Palate.  —  The  hard  palate,  formed  by  the  palatine 
plates  of  the  maxillary  and  palate  bones,  is  a  resisting  surface 
for  the  tongue  in  tasting,  in  mastication,  in  deglutition,  and  in 
the  articulation  of  sounds.  The  tissue  covering  the  bones  is 
thick  and  close  in  texture,  and  firmly  united  to  the  asperities  on 
the  bones.  But  it  is  not  everywhere  of  equal  thickness.  Along 
the  raph^  in  the  mesial  line  it  is  much  thinner  than  at  the 
sides  ;  for  this  reason,  the  hard  palate  is  in  this  situation  more 
prone  to  be  perforated  in  syphilitic  disease. 


MECHANISM    OF    DEGLUTITION.  25 1 

A  thick  layer  of  glands  {glanditlce  palatince)  is  arranged  in 
rows  on  cither  side  of  the  hard  palate.  These  glands  become 
more  numerous  and  larger  towards  the  soft  palate.  Their  ori- 
fices are  visible  to  the  naked  eye.  The  mucous  membrane  has 
a  very  thick  epithelial  coat,  which  gives  the  white  color  to  the 
palate.  The  descending  palatine  branch  of  the  internal  maxil- 
lary artery,  and  the  palatine  nerves  from  the  maxillary,  may  be 
traced  along  each  side  of  the  roof  of  the  mouth.  The  ramifica- 
tions of  these  arteries  and  nerves  supply  the  soft  as  well  as  the 
hard  palate. 

Mechanism  of  Deglutition. — With  the  anatomy  of  the 
parts  fresh  in  your  mind,  consider  for  a  moment  the  mechanism 
of  deglutition.  The  food,  duly  masticated,  is  collected  into  a 
mass  upon  the  back  of  the  tongue ;  the  mandible  is  then  closed 
to  give  a  fixed  point  for  the  action  of  the  muscles  which  raise 
the  OS  hyoides  and  larynx,  and  the  food  is  carried  back  into  the 
pharynx  by  the  pressure  of  the  tongue  against  the  palate,  at 
the  same  time  that  the  pharynx  is  elevated  and  expanded  to 
receive  it  (by  the  stylo-pharyngei  on  each  side).*  The  food, 
having  reached  the  pharynx,  is  prevented  from  ascending  into 
the  nasal  passages  by  the  approximation  of  the  posterior  pala- 
tine arches  and  the  elevation  of  the  soft  palate,  which  thus 
forms  a  horizontal  temporary  roof  to  the  pharynx;  it  is  pre- 
vented from  returning  into  the  mouth  by  the  pressure  of  the 
retracted  tongue  and  the  contraction  of  the  anterior  palatine 
arches  :  it  cannot  enter  the  larynx,  because  its  upper  opening 
is  closed  and  protected  by  the  falling  of  the  epiglottis  ;  f  conse- 
quently, being  forcibly  compressed  by  the  constrictors  of  the 
pharynx,  the  food  passes  into  the  oesophagus,  through  which  it  is 
conveyed  into  the  stomach  by  the  undulatory  contraction  of  that 
tube. 

The  food  passes  with  different  degrees  of  rapidity  through  the 
different  parts  of  its  course,  but  most  rapidly  through  the 
pharynx.  The  necessity  of  this  is  obvious,  as  the  air-tube  must 
be  closed  while  the  food  passes  over  it,  and  the  closure  pro- 
duces a  temporary  interruption  to  respiration.  The  progress 
of  the  food  through  the  oesophagus  is  slow  and  gradual. 

*  The  larynx  being  also  elevated  and  drawn  forwards,  a  greater  space  is  thus 
left  between  it  and  the  vertebrae  for  the  distention  of  the  pharynx. 

t  This  falling  of  the  epiglottis  is  effected,  not  by  special  muscular  agency,  but 
by  the  simultaneous  elevation  of  the  larynx  and  the  retraction  of  the  tongue.  A 
perpendicular  section  through  all  the  parts  concerned  is  necessary  to  show  the 
working  of  this  mechanism. 


252  DISSECTION    OF    THE    LARYNX. 


DISSECTION    OF   THE    LARYNX. 

Situation  and  Relations.  —  The  larynx  is  the  upper  dilated 
part  of  the  windpipe,  in  which  phonation  takes  place.  It  con- 
sists of  numerous  cartilages  articulated  together  to  form  an 
open  tube,  and  to  protect  the  delicate  structures  concerned  in 
vocalization. 

It  forms  a  prominence  in  the  middle  line  of  the  neck,  cov- 
ered in  front  by  the  integument  and  cervical  fasciae,  the  sterno- 
hyoid, sterno-thyroid,  and  thyro-hyoid  muscles,  and  the  thyroid 
body.  It  has  the  large  vessels  of  the  neck  on  each  side. 
Above,  it  is  attached  to  the  hyoid  bone ;  below,  it  is  continuous 
with  the  trachea ;  behind  it  is  the  pharynx,  into  the  anterior 
part  of  which  it  opens. 

Before  commencing  the  dissection  of  the  larynx  the  student 
should  make  himself  acquainted  with  the  cartilages  which  com- 
pose it  and  the  ligaments  which  connect  them,  as  seen  in  a  dry 
preparation. 

Os  Hyoides.  —  This  bone,  named  from  its  resemblance  to 
the  Greek  Upsilon,  is  situated  between  the  larynx  and  the 
tongue,  and  serves  for  the  attachment  of  the  muscles  of  the 
tongue.  It  may  be  felt  immediately  below,  and  one  inch  and  a 
half  {J.8  cm.)  behind,  the  symphysis  of  the  mandible.  It  is 
arched  in  shape,  and  consists  of  a  body,  two  greater  and  two 
lesser  cornua.  The  body  (basi-hyal)  is  the  thick  central  portion. 
Its  anterior  surface  is  convex  and  has  a  median  vertical  ridge, 
on  each  side  of  which  are  depressions  for  the  attachments  of 
muscles ;  its  posterior  surface  is  smooth,  deeply  concave,  and 
corresponds  to  the  epiglottis.  The  greater  cormia  {tJiyro-hyals), 
right  and  left,  project  backwards  for  about  an  inch  and  a  half 
{^.8  cjn.),  with  a  slight  inclination  upwards,  and  terminate  in 
blunt  ends  tipped  with  cartilage.  In  young  subjects  they  are 
connected  to  the  body  of  the  bone  by  fibro-cartilage ;  this,  in 
process  of  years,  becomes  ossified.  The  lesser  cornua  {cerato- 
hyals)  are  connected,  one  on  each  side,  to  the  point  of  junction 
between  the  body  and  the  greater  cornua,  by  means  of  a  little 
joint  lined  with  synovial  membrane,  which  admits  of  free  motion. 
They  are  of  the  size  of  a  barley-corn,  and  give  attachment  to 
the  stylo-hyoid  ligaments  (Fig.  91). 

Ligaments.  —  The  os  hyoides  is  connected  with  the  thyroid 
cartilage   by   several    ligaments,   which    contain   a   quantity  of 


THVKOin    CARTILAGE.  253 

elastic  tissue.  There  is  :  i .  The  tJiyro-hyoid  membrane,  a  broad 
fibrous  membrane,  which  proceeds  from  the  superior  border  of 
the  thyroid  cartilage  to  the  upper  and  posterior  part  of  the 
hyoid  bone.  In  front  of  this  membrane 
there  is  a  bursa,  of  which  the  use  is  to 
facilitate  the  play  of  the  thyroid  cartilage 
behind  the  os  hyoides.  The  central  por- 
tion is  stronger  than  the  lateral,  and  is 
called  the  anterior  thyro-Jiyoid  ligament. 
Through  the  lateral  part  of  this  membrane 

,1  •  1  1 „        1  i„  Fig.  gi.  —  Anterior  View  of 

the   superior  laryngeal   nerve   and    artery  ^  os  hyoides. 

enter  the  larynx.      2.  The  right  and  left    i,i.  Anterior  or  con  vex  surface 

,  ,,  ■,.,,.  .11  of  'l>e  body.     2,  2.  Clreater 

lateral   tliyro-liyoid   ligaments    extend    be-      comua.  3,3.  Articulation  of 

.  ,1  ^  "j.-  r  ti-      _         4.  the  ereater  cornua  with  the 

tween  the  extremities  of  the  greater  cornua      body.  4,4.  Lesser  comua. 
of  the  OS  hyoides  and  the  ascending  cornua 

of  the  thyroid  cartilage.      They  contain  a  small  nodule  of  carti- 
lage {corpus  triticenm). 

Cartilages  of  the  Larynx. — The  framework  of  the  larynx 
is  composed  of  nine  cartilages,  viz.,  the  thyroid,  the  cricoid,  the 
two  arytenoid,  the  two  cornicula  laryngis,  the  two  cuneiform 
cartilages,  and  the  epiglottis.  These  are  connected  by  joints 
and  elastic  ligaments,  so  that  they  can  be  moved  upon  each 
other  by  their  respective  muscles ;  the  object  of  this  motion 
being  to  act  upon  two  elastic  ligaments,  called  the  vocal  cords 
or  bands,  upon  the  vibration  of  which  phonation  depends. 

Thyroid  Cartilage. — This  cartilage,  so  called  because  it 
shields  the  mechanism  behind  it,  consists  of  two  lateral  halves 
(ales),  united  at  an  acute  angle  in  front,  which  forms  the  prom- 
inence termed  the  pomum  Adami.  This  prominence  presents 
a  notch  at  its  upper  part,  to  allow  it  to  play  behind  the  os 
hyoides  in  deglutition.  There  is  a  bursa  in  front  of  it.  Each 
ala  is  somewhat  quadrilateral  in  form,  and  presents  for  examina- 
tion two  surfaces  and  four  borders.  The  outer  surface  of  each 
ala  is  marked  by  an  oblique  line  passing  downwards  and  forwards 
from  the  base  of  the  upper  cornu,  which  gives  attachment  to 
the  sterno-thyroid  and  thyro-hyoid  muscles.  The  smooth  sur- 
face behind  the  ridge  gives  attachment  to  the  inferior  constrictor. 
The  inner  siwface  is  smooth,  slightly  concave,  and  is  covered 
with  mucous  membrane.  In  the  acute  angle  in  front  there  are 
attached  from  above  downwards  the  epiglottis,  the  false  or 
ventricular  bands,  and  true  vocal  cords  or  bands,  the  thyro- 
arytenoidei  and  thyro-epiglottidei  muscles.     The  inferior  border 


2  54  LIGAMENTS. 

is  slightly  arched  in  the  middle,  affording  attachment  to  the 
crico-thyroid  membrane,  and  on  either  side  presents  a  convex 
prominence,  which  gives  attachment  to  the  crico-thyroid  muscle 
and  the  crico-thyroid  membrane.  The  siipn'ior  border  is  nearly 
horizontal,  and  affords  attachment  to  the  thyro-hyoid  membrane. 
The  posterior  border  is  thick,  rounded,  and  nearly  vertical,  and 
gives  insertion  to  the  stylo-pharyngeus  and  palato-pharyngeus 
muscles.  This  border  terminates,  above  and  below,  in  round 
projections  called  the  tipper  and  Iczvcr  cormia.  The  upper  is 
the  longer ;  the  lower  articulates  with  the  side  of  the  cricoid 
cartilage  (Figs.  92,  93). 

Cricoid  Cartilage.  —  This  cartilage,  named  from  its  resem- 
blance to  a  ring,  is  situated  below  the  thyroid.  It  is  not  of 
equal  depth  all  round.  It  is  narrow  in  front,  where  it  may  be 
felt  about  a  quarter  of  an  inch  {6  mm)  below  the  thyroid  ;  from 
this  part,  the  upper  border  gradually  rises,  so  that,  posteriorly, 
the  ring  is  an  inch  (2.^  cm)  in  vertical  depth,  and  occupies  part 
of  the  interval  left  between'  the  alse  of  the  thyroid.  In  the  mid- 
dle of  this  broad  posterior  surface  is  a  vertical  ridge,  on  either 
side  of  which  observe  a  superficial  excavation  for  the  origin  of 
the  crico-arytenoidei  postici ;  to  the  lower  part  of  the  vertical 
ridge  are  attached  some  of  the  longitudinal  fibres  of  the  oesoph- 
agus. On  its  upper  part  are  two  oval  slightly  convex  surfaces 
for  the  articulation  of  the  arytenoid  cartilages,  between  which  is 
a  concavity  for  the  attachment  of  the  arytenoideus.  In  front, 
its  upper  l3order  presents  a  broad  excavation  to  which  the  crico- 
thyroid membrane  (on  which  is  seen  the  crico-thyroid  artery),  is 
attached.  On  its  outer  surface,  external  to  the  depression  for 
the  crico-arytenoideus  posticus,  is  an  elevated  facet  which  artic- 
ulates with  the  inferior  cornu  of  the  thyroid  cartilage.  In  front 
of  this  articular  surface  it  gives  attachment  to  the  inferior  con- 
strictor of  the  pharynx.  The  lower  border  is  straight,  and  is 
connected  by  fibrous  membrane  to  the  first  ring  of  the  trachea. 
The  inner  surface  is  smooth,  and  the  upper  border  is  elliptical, 
its  lower  being  nearly  circular.      (Figs.  92,  93.) 

Ligaments.  —  The  thyroid  cartilage  is  connected  to  the  cri- 
coid by  a  membrane — the  crico-thyroid.  It  consists  of  a  me- 
dian triangular  portion,  composed  mainly  of  elastic  tissue,  with 
its  base  directed  downwards.  The  lateral  portions  are  thin  and 
membranous,  extending  as  far  backwards  as  the  articular  facets 
for  the  thyroid  cartilage,  and  are  intimately  connected  with  the 
inferior  vocal  cords  or  vocal  bands.      Between  the  inferior  cornu 


ARYTENOID  CARTILAGES. 


255 


of  the  thyroid  cartilage  and  the  cricoid  there  is  a  distinct  joint, 
having  a  synovial  membrane,  and  strengthened  by  a  capsular 
ligament.  The  articulation  allows  of  a  movement  revolving 
upon  its  own  axis,  and,  consequently,  permits  the  approxima- 
tion of  the  two  cartilages.     (Fig.  94,  p.  259). 


Jng,crir 
tra(Qi. 


Fig.  92.  —  Larynx,  Front  View,  with  the  Liga- 
ments AND  Insertion  of  Muscles. 

O.  h.,  Os  hyoides  ;  C.  th..  Thyroid  cartilage  ;  Corp. 
trit..  Corpus  triticeum  ;  C.  c.^  cricoid  cartilage  ;  C. 
tr..  Tracheal  cartilage;  Lig.  ihyr.-hyoid  vied.. 
Middle  thyro-hyoid  ligament :  Lig.  th.-h.  Int.,  Lat- 
eral thyro-hyoid  ligament  ;  Lig.  cric.-thyr.  tned., 
Middle  crico-thyroid  ligament;  Lig.  cric.-irach., 
Crico-tracheal  ligament;  7t/. /j.-/z.,  Sterno-hyoideus 
muscle;  AI.  //(.-//^'Cirf.,  Thyro-Hyoideus  muscle;  M. 
j/. -//;.,  Sterno-thyroideus  muscle.  HL  cr.-th. ,  Crico- 
thyroideus  muscle. 


Fig.  g3. —  Posterior  View  of  the  Lar- 
ynx, with  the  Muscles  Removed. 

£■.,  Epiglottis  cushion  (W.>;  L.  ar.-c/>., 
Aryteno-epiglottic  fold  or  ligament;  M. 
»«.,  Membrana  mucosa;  C.  II'.,  Cartilage 
of  Wiisberg  or  cuneiform;  C.  S.,  Carti- 
lage of  Santorini  or  cornicula  laryngis  ; 
C.  aryt..  Arytenoid  cartilage  ;  C.  c, 
Cricoid  cartilage  ;  /'.  >ir.,  Muscular  pro- 
cess or  external  angle  ;  L  .  cr.-ar..  Crico- 
arytenoid ligament  ;  C.  s.,  Superior 
cornu  ;  C.  i.,  Inferior  cornu  of  the  thyroid 
cartilage;  L.  ce.-cr.  p.  i. ,  Posterior  in- 
ferior cerato-cricoid  ligament  ;  C.  tr.. 
Tracheal  cartilage;  P.  in.  tr.,  Membra- 
nous portion  of  the  trachea. 


Arytenoid  Cartilages.  —  These  cartilages  are  situated,  one 
on  each  side,  at  the  back  of  the  upper  border  of  the  cricoid  car- 
tilage. In  the  recent  state,  before  the  membranes  and  muscles 
have  been  removed,  the  space  between  them  resembles  the  lip 
of  a  pitcher ;  hence  their  name.     Each  is  pyramidal,  with  the 


256  EPIGLOTTIS. 

apex  upwards,  is  about  one-half  of  an  inch  (/J  imn.)  in  height, 
and  one-quarter  of  an  inch  [6  vim.)  in  diameter  at  its  base,  and 
presents  for  examination  three  surfaces  (marked  off  by  three 
borders),  a  base  and  an  apex.  The  posterior  surface  of  each  is 
triangular  and  concave,  and  gives  attachment  to  the  arytenoid- 
eus  muscle  ;  the  anterior  surface  is  irregular  and  convex,  afford- 
ing attachment  to  the  thyro-arytenoideus,  and  to  the  ventricular 
bands  or  false  vocal  cord;  the  internal  surface,  the  narrowest 
and  nearly  flat,  faces  the  corresponding  surface  of  the  opposite 
cartilage,  and  is  covered  with  mucous  membrane.  The  base  is 
broad,  and  presents  a  smooth,  somewhat  concave,  triangular  sur- 
face, which  articulates  with  the  cricoid  cartilage  ;  in  front  of  the 
base  is  the  pointed  anterior  angle,  which  gives  attachment  to 
the  true  vocal  cord  or  vocal  bands,  and  contributes  to  form  part 
of  the  boundary  of  the  rima  glottidis  ;  at  the  outer  and  back 
part  of  the  base  is  the  external  angle,  into  which  certain  muscles 
moving  the  cartilage  are  inserted,  viz.,  the  crico-arytenoideus 
posticus  and  crico-arytenoideus  lateralis.  The  base  is  articu- 
lated with  the  cricoid  by  a  joint  which  has  a  loose  capsular  liga- 
ment and  a  synovial  membrane,  permitting  motion  in  all  direc- 
tions, like  the  first  joint  of  the  thumb.  The  apex  is  truncated 
and  points  backwards  and  inwards.  It  is  surmounted  by  a  car- 
tilaginous nodule,  called  the  corniculum  laryngis. 

Cornicula  Laryngis.  — Are  two  small  conical  cartilaginous 
nodules,  and  continue  the  direction  of  the  arytenoid  cartilages 
upwards  and  inwards. 

Cuneiform  Cartilages.  —  These  cartilages,  sometimes  called 
the  cartilages  of  Wrisberg,  are  conical  in  form,  and  somewhat 
curved,  with  their  broader  part  directed  upwards  and  forwards. 
They  are  contained  in  the  aryteno-epiglottic  fold.   (Fig.  95,  p.  260). 

Epiglottis.  — This  piece  of  yellow  fibro-cartilage  is  situated 
in  the  middle  line,  and  projects  over  the  larynx  like  a  valve.  It 
is  like  a  leaf  with  its  stalk  directed  downwards.  Its  ordinary 
position  is  perpendicular,  leaving  the  upper  opening  of  the 
larynx  free  for  respiration  ;  but  during  the  elevation  of  the  lar- 
ynx in  deglutition  it  becomes  horizontal,  falls  downwards  and 
backwards  over  the  larynx,  and  prevents  the  entrance  of  food 
into  it.  This  descent  of  the  epiglottis  is  accomplished,  not  by 
special  muscular  agency,  but  by  the  simultaneous  elevation  of 
the  larynx  and  the  retraction  of  the  tongue.  Its  apex  or  lower 
part  is  attached  by  the  thyro-cpiglottic  ligament  to  the  angle  of 
the  thyroid  cartilage  ;  it  is  also  connected  by  an  elastic  ligament, 


MUCOUS    MEMI5KANE    OF    THE    LARYNX.  257 

hyo-cpiglottic,  to  the  posterior  surface  of  the  os  hyoicles.  Later- 
ally, its  borders  are  rather  turned  backwards,  and  to  them  are 
attached  two  folds  of  mucous  membrane,  which  pass  to  the  ary- 
tenoid cartilages,  called  the  arytcjio-cpiglottic  folds.  Its  ante- 
rior surface  is  only  free  at  its  base,  where  it  is  connected  with 
the  base  of  the  tongue  by  the  three  glosso-epiglottic  folds.  Its 
posterior  or  laryngeal  surface  is  smooth,  concavo-convex  and 
free,  and  looks  towards  the  larynx.  The  surface  of  the  epiglot- 
tis is  closely  invested  by  mucous  membrane ;  this  being  re- 
moved, the  yellow  cartilage  of  the  epiglottis  is  seen  pitted  and 
often  perforated  by  the  small  mucous  glands. 

The  cartilages  of  the  larynx  resemble  those  of  the  ribs  in 
structure.  In  the  young  they  are  dense  and  elastic,  but  some 
have  a  tendency  to  ossify  with  age.  In  very  old  subjects  the 
thyroid  and  cricoid  cartilages  are  often  completely  ossified,  and 
their  interior  presents  an  areolar  tissue,  containing  oily  matter, 
analogous  to  the  spongy  texture  of  the  bones.  The  epiglottis, 
cornicula  laryngis,  and  cuneiform  cartilages  are  rarely  ossified, 
on  account  of  their  consisting  of  yellow  fibro-cartilage  resem- 
bling that  of  the  ear  and  nose. 

The  larynx  must  now  be  examined  in  its  perfect  condition. 

Mucous  Membrane  of  the  Larynx.  —  The  mucous  mem- 
brane lines  the  whole  of  the  interior  of  the  larynx,  being  con- 
tinuous above  with  that  of  the  pharynx  and  mouth,  below  with 
that  of  the  trachea.  It  is  intimately  adherent  to  the  posterior 
part  of  the  epiglottis  and  to  the  true  vocal  bands  or  cords  ;  else- 
where it  is  loosely  connected  to  the  subjacent  structures  by  an 
abundance  of  areolar  tissue,  which  admits  of  its  being  elevated 
into  large  folds.  This  is  chiefly  found  about  the  upper  opening 
of  the  larynx,  and  it  deserves  notice  from  the  rapidity  with 
which  it  becomes  the  seat  of  serous  effusion  in  acute  inflamma- 
tion of  the  larynx,  and  thus  produces  symptoms  of  suffocation. 
In  the  remaining  part  of  the  interior  of  the  larynx  the  mucous 
membrane  is  moderately  adherent  to  the  subjacent  tissues,  and 
at  the  ventricular  band  or  false  vocal  cord  it  reduplicates  upon 
itself  and  then  lines  the  sacculus  laryngis.  Naturally,  the  mu- 
cous membrane  is  of  pale  rose  color,  except  where  it  covers  the 
cushion  of  the  epiglottis,  where  it  is  bright  pink.  It  is  covered 
by  columnar  ciliated  epithelium  below  the  ventricular  bands  or 
false  vocal  cords,  and  this  variety  is  continued  up  the  epiglottis 
as  high  as  its  middle ;  above  this,  by  squamous  epithelium. 
From  the  root  of  the  tongue  to  the  anterior  surface  of  the  epi- 


258  SUPERIOR  OPENING  OF  THE  LARYNX. 

glottis,  the  membrane  forms  three  folds,  glosso-epiglottic,  one 
median,  and  two  lateral,  containing  elastic  tissue.  From  the 
epiglottis,  to  which  it  is  intimately  adherent,  it  is  continued 
backwards  on  either  side  to  the  apices  of  the  arytenoid  cartilages, 
forming  the  aryteno-epiglottic  folds  which  bound  the  upper  en- 
trance into  the  larynx. 

The  mucous  membrane  of  the  larynx  is  remarkable  for  its 
acute  sensibility.  This  is  requisite  to  guard  the  upper  opening 
of  the  larynx  during  the  passage  of  the  food  over  it.  The 
larynx  is  closed  during  the  act  of  deglutition ;  but  if,  during 
this  process,  anyone  attempt  to  speak  or  laugh,  the  epiglottis  is 
raised,  and  allows  the  food  to  pass,  as  it  is  termed,  the  wrong 
way.  As  soon  as  the  foreign  body  touches  the  mucous  mem- 
brane of  the  larynx  a  spasmodic  fit  of  coughing  expels  it. 

The  sub-mucous  tissue  of  the  larynx  is  studded  with  mucous 
glands.  An  oblong  mass  of  them  lies  in  the  aryteno-epiglottic 
fold,  and  they  are  particularly  numerous  about  the  ventricles  of 
the  larynx.  The  surface  of  the  epiglottis  towards  the  tongue  is 
abundantly  provided  with  them.  Their  ducts  pass  through  the 
epiglottis,  and  may  be  recognized  as  minute  openings  on  its 
laryngeal  aspect. 

Superior  Opening  of  the  Larynx.  —  This  is  the  opening 
through  which  the  larynx  communicates  with  the  pharynx.  Its 
outline  is  triangular,  with  its  base  directed  forwards,  and  it 
slopes  from  before  backwards.  Anteriorly  it  is  bounded  by  the 
epiglottis,  laterally  by  the  aryteno-epiglottic  folds  and  cuneiform 
cartilages,  posteriorly  by  the  arytenoid  cartilages  and  the  cornic- 
ula  laryngis.  The  apex  presents  the  funnel-shaped  appearance 
from  which  the  arytenoid  cartilages  derive  their  name. 

On  looking  down  through  this  superior  opening  you  see  the 
cavity  of  the  larynx,  which  is  divided  into  an  upper  and  a  lower 
part  by  the  narrow  triangular  fissure,  called  the  glottis,  or  lima 
glottidis ;  so  that  the  upper  part  gradually  narrows  to  this 
chink,  while  the  lower  part  gradually  widens  and  becomes  con- 
tinuous at  the  lower  border  of  the  cricoid  cartilage  with  the 
trachea. 

The  objects  seen  above  the  rima  glottidis  are,  in  the  middle 
line,  below  the  base  of  the  epiglottis,  a  round  elevation  covered 
with  mucous  membrane  of  a  bright  pink  color,  termed  the 
ais/iioH  of  the  epiglottis  ;  on  each  side  is  an  arched  fold,  the 
ventricular  bands  or  false  vocal  cords,  with  their  concavity  look- 
ing downwards,  and   ff)rming   the   upper  boundary  of   a   small 


VOCAL    HANDS. 


259 


recess,  the  ventricle  of  tJie  larynx,  leading  into  a  pouch,  called 
the  sacculiis  laryngis  ;  below  this  are  the  two  white  bands,  the 
vocal  bands  or  true  vocal  cords,  which  form  the  boundaries  of 
the  glottis.  The  larynx  below  the  vocal  bands  gradually  en- 
larges and  presents  nothing  calling  for  special  description. 

Glottis,  or  Rima  Glottidis. —  The  rima  glottidis  is  the 
triangular  horizontal  opening  between  the  vocal  bands.  Its 
apex  is  directed  forwards,  its  base  backwards.  The  anterior 
two-thirds  of  this  opening  is  bounded  by  the  vocal  bands,  the 
posterior  third  by  the  arytenoid  cartilages.  The  length  in  the 
male  is  nearly  an  inch  (2^  mm),  its  width  at  rest  from  one- 
fourth  to  one-third  of  an  inch  {6  to  8  mm.)  ;  in  the  female  its 
length  is  two-thirds  of  an  inch  {16  mm),  its  width  one-sixth  of 
an  inch  (./  mm).  Before  the  age  of  puberty  these  dimensions 
are  much  less. 

Ventricular  Bands. — These  are  the  prominent  crescentic 
folds  of  mucous  membrane  which  form  the  upper  boundaries  of 
the  ventricles  and  inclose  within  them  thin  ligamentous  fibres, 
called  the  superior  thyro-arytenoid  ligaments.  They  are  called 
the  false  vocal  cords  because  they  have  little  or  nothing  to  do 
with  the  production  of  the  voice.  They  are  composed  of  elastic 
tissue  like  the  vocal  bands  ;  but  they  also  contain  fatty  tissue, 
which  the  vocal  bands  do  not. 

Vocal  Bands.* — These  two  bands,  called  also  the  inferior 
thyro-arytenoid  ligaments,  are  composed  of  yellow  elastic  tissue, 
and  extend  horizontally  from  the 
angle  of  the  thyroid  cartilage 
to  the  anterior  angles  of  the 
base  of  the  arytenoid  cartilages. 
Their  inner  or  free  edges  are 
thin  and  sharp,  and  look  up- 
wards ;  their  outer  borders  are 
continuous  with  the  crico-thyroid 
membrane,  and  are  in  contact 
with  the  thyro-arytenoidei  mus- 
cles. They  diverge  as  they  pass 
backwards,  and  are  covered  with  very  thin  and  closely  adherent 
mucous    membrane,    having    columnar   epithelium.      We    shall 


Thyroid  cartilage. 
Vocal  bands. 


Arytenoid  carti- 
lage. 

Elastic  ligament. 


Fig.  <34.  —  Shape  of  thb   Glottis  when 
AT  Rest. 


[  *  The  editor  desires  to  emphasize  the  change  of  cord  to  band,  false  vocal  to 
ventricular,  for  anatomical  reasons  which  to  any  dissector  are  apparent.  Ventric- 
ular tmnd  locates  the  position  and  does  away  with  the  explanation  that  this  por- 
tion has  nothing  to  do  with  pho nation.  —  A.  H.] 


26o 


VOCAL    BANDS, 


presently  see  that,  by  the  muscles  which  act  upon  the  arytenoid 
cartilages,  these  bands  can  be  approximated  or  separated  from 
each  other ;  in  other  words,  the  rima  glottidis  can  be  closed  or 
dilated.  When  sufficiently  tightened,  and  brought  parallel  by 
means  of  certain  muscles,  the  bands  are  made  to  vibrate  by  the 
current  of  the  expired  air,  and  thus  is  produced  sound. 


Fig.  9$. —  Posterior  View  of  the  Larynx,  with  its  Muscles. 

.,  Epiglottis,  with  tlie  cushion  (W.)  ;  C.  IV.,  Cartilage  of  Wrisberg  ;  C.S.,  Cartilage  of  Santorini  ; 
Cari.  eric,  Cricoid  cartilage  ;  Corttii  sup.,  Superior  cornua  of  the  thyroid  cartilage  M.  ar.  tr. 
Transverse  portion  of  the  arytenoideus  ;  Mm.  ar.  obi.,  Oblique  portion  of  the  arytenoideus  . 
RL  cr.  aryt.  post.,  Crico-arytenoideus  muscle  ;  Pars  cart..  Cartilaginous  rings  of  the  tracliea  ; 
Pars  metnb.,  Traclieal  membrane. 


In  the  adult  male  the  vocal  bands  measure  about  seven- 
twelfths  of  an  inch  (/</  ;«;«.)  ;  in  the  female  about  five-twelfths 
of  an  inch  (//  mm),  In  boys  they  are  shorter  ;  hence  their 
peculiar  voice.  At  puberty  the  bands  lengthen  and  the  voice 
breaks. 

The  glottis  admits  of  being  dilated,  contracted,  and  even  com- 
pletely closed,  by  its  appropriate  muscles.  When  at  rest  its 
shape  is  triangular,  as  shown  in  Fig.  94,  where  the  arytenoid 


VENTRICLES  OF  THE  LARYNX. 


261 


cartilages  are  cut  through  on  a  level  with  the  vocal  cords.  Dur- 
ing every  inspiration  the  glottis  is  dilated  by  the  crico-aryte- 
noidei  postici ;  it  then  becomes  pear-shaped  (Fig.  97).  During 
expiration  it  resumes  its  triangular  shape,  and  this  return  to  a 


Arytenoid  cartilage. 
Crico-arytenoid  joint. 

Crico-thyroid  joint. 


Thyroid  cartilage. 


Vocal  band. 


Cricoid  cartilage  raised. 
Cricoid  cartilage. 


Fig.  96. —  Diagram  Showing  the  Action  of  the  Crico-thyroid  Muscle. 


state  of  rest  is  effected,  not  by  muscular  agency,  but  by  two 
elastic  ligaments  shown  in  Fig.  94,  which  draw  the  arytenoid 
cartilages  together.  Thus,  then,  the  glottis,  like  the  chest,  is 
dilated  by  nmsciilar  tissue  ;  like  the  chest,  also,  it  is  contracted 
by  elastic  tissue.     In  speaking  or  singing  the  glottis  assumes 


Vocal  band. 

Thyroid  cartilage. 
Cricoid  cartilage. 


Arytenoid  cartilage. 
Elastic  ligament 
(crico-arytenoid). 


Thyro-arytenoideus. 


Crico-arytenoideus 
lateralis. 


Ideal  pivot. 


Crico-arytenoideus 
posticus. 


Fig.  97. —Glottis  Dilated;  Muscles  Dilating  it  Represented  Wavy. 


what  is  called  the  vocalizing  position  — that  is,  the  opening  be- 
comes narrower,  and  its  edges  nearly  parallel. 

Ventricles  of  the   Larynx. — These  are  the   recesses  be- 
tween the   ventricular  and   vocal   bands,  and  each  leads   to    a 


262 


M.    CRICO-ARYTENOIDEUS    POSTICUS. 


small  conical  pouch,  the  sacculns  laryngis.  Each  ascends  for 
about  half  an  inch  (/J  mm},,  as  high  as  the  upper  border  of  the 
thyroid  cartilage,  which  bounds  it  on  its  outer  side,  while  on  the 
inner  side  is  the  ventricular  band.  It  contains  from  sixty  to 
seventy  muciparous  glands.  Over  its  inner  and  upper  part  is  a 
layer  of  muscular  tissue,  compressor  saccidi  laryngis  of  Hilton 
(aryteno-epiglottideus  inferior),  which  connects  it  with  the  ary- 

teno-epiglottic  fold ;  on  its  outer 
side  is  the  upper  part  of  the  thyro- 
arytenoideus. 

Intrinsic  Muscles  of  the  Lar- 
ynx.—  There  are  eleven  muscles 
which  act  upon  the  larynx,  five  on 
each  side  and  one  in  the  middle. 
The  five  pairs  are  the  crico- 
thyroidei,  the  crico-arytenoidei 
postici,  the  crico-arytenoidei  lat- 
erales,  the  thyro-arytenodei,  and 
the  aryteno-epiglottidei.  The 
single  one  is  the  arytenoideus. 

M.  Crico-thyroideus.  —  This 
muscle  is  situated  on  the  front  of 
the  larynx.  It  aiiscs  from  the 
front  and  side  of  the  cricoid  carti- 
lage, ascends  obliquely  outwards, 
and  is  inserted  into  the  inferior 
border  and  lower  cornu  of  the  thy- 
roid. Its  action  is  to  tighten  the 
vocal  cords.  It  does  this  by  rais- 
ing the  anterior  part  of  the  cricoid 
cartilage,  since  this  cartilage  cannot 
be  raised  without  lengthening  these 
cords,  as  shown  by  the  dotted  line, 
Fig.  96.  Its  nerve  is  the  external  laryngeal  branch  of  the  supe- 
rior laryngeal.  Between  the  anterior  borders  of  the  two  mus- 
cles is  seen  the  crico-thyroid  membrane,  which  is  divided  in 
laryngotomy. 

M.  Crico-arytenoideus  Posticus.  —  This  muscl«  arises 
from  the  broad  depression  on  the  posterior  part  of  the  cricoid 
cartilage;  its  fibres  converge  and  pass  outwards  and  upwards, 
to  be  inserted  into  the  outer  angle  of  the  base  of  the  arytenoid 
(Fig.  95  p.  260).  Its  action  is  to  dilate  the  glottis.     It  does  this  by 


Fig.  98. 


■Side  View  oe  the  Muscles 
OP  THE  Larynx. 


.  Thyro-epiglottideus.  2.  Thyro-ary- 
tenoideus,  upper  and  lower  portions. 
3.  Crico-arytenoideus  lateralis.  4.  Crico- 
arytenoideus  posticus.   5.  Arytenoideus. 


M.    CKICO-ARVTENOIDEUS    LATERALIS. 


263 


drawing  the  posterior  tubercle  of  the  arytenoid  cartilage  towards 
the  mesial  line,  and  therefore  the  anterior  angle  (to  which  the 
vocal  cord  is  attached)  froui  the  mesial  line  (Fig.  97).  In  this 
movement  the  arytenoid  cartilage  rotates  as  upon  a  pivot,  and 
acts  as  a  lever  of  the  first  order,  the  fulcrum  or  ideal  pivot 
being  intermediate  between  the  power  and  the  weight.  This 
muscle  dilates  the  glottis  at  each  inspiration.  Its  nerve  comes 
from  the  inferior  laryngeal. 

M.  Arytenoideus. — This  single  muscle  is  situated  imme- 
diately at  the  back  of  the  arytenoid  cartilages.  The  fibres  pass 
across  from  one  cartilage  to  the  other,  running  in  a  transverse 
direction.  Action.  —  By  approximating  the  arytenoid  cartilages, 
they  assist  in  contracting  the  glottis.  It  is  supplied  by  the 
inferior  laryngeal  7ierve. 


Vocal  band. 


Arytenoid  cartilage. 
Elastic  ligament. 


Thyro-arytenoideus. 


Crico-arytenoideus 
lateralis. 


Crico-arytenoideus 
posticus. 


Fig.  99.  —  Glottis  Closed;  Muscles  Closing  it  Represented  Wavv. 


M.  Aryteno-epiglottis.  —  This  muscle  arises  from  the  infe- 
rior and  outer  angle  of  the  arytenoid  cartilage,  and,  crossing  its 
fellow  like  the  letter  X,  is  inserted  partly  into  the  apex  of  the 
opposite  arytenoid  cartilage  and  partly  into  the  aryteno-epiglottic 
fold.  This  is  sometimes  spoken  of  as  part  of  the  aryte- 
noideus. 

M.  Crico-arytenoideus  Lateralis.  —  To  expose  this  muscle 
reflect  the  crico-thyroid  muscle,  the  crico-thyroid  membrane,  and 
then  cut  away  the  ala  of  the  thyroid  cartilage.  It  arises  from 
the  upper  border  of  the  side  of  the  cricoid  cartilage,  and  the 
fibres,  passing  backwards  and  upwards,  converge  to  be  inserted 
into  the  external  angle  of  the  base  of  the  arytenoid,  in  front  of 
the  cricoid-arytenoideus  posticus.  Actioji.  —  By  drawing  the 
arytenoid  cartilages  inwards,  the  muscles  of  opposite  sides  con- 


264 


M.    THYRO-ARYTENOIDEUS. 


tract  the  glottis  (Fig.  99).      Its  nerve  comes  from  the  inferior 
laryngeal. 

M.  Thyro-arytenoideus. — This  muscle  arises  from  the 
side  of  the  angle  of  the  thyroid  cartilage  and  the  crico-thyroid 
membrane,  runs  horizontally  backwards,  and  is  inserted  into  the 
base  and  anterior  surface  of  the  arytenoid.  Its  fibres  run  par- 
allel with  the  true  vocal  cord,  and  some  of  them  are  directly 


Fig.  100.  —  Nerves  of  the  Larynx. 


O.  h.,  Os  hyoides  ;  C.  th.,  Thyroid  cartilage  ;  C.  C,  Cricoid  cartilage  ;  Tr.,  Trachea  ;  M.  ih  -ar., 
Thyro-arytenoideus  muscle  ;  M.  cr.-ar.  p.,  Posterior  crico-arytenoideus  muscle  ;  1\I.  cr  -ar  L., 
Lateral  crico-arytenoideus  muscle  ;  M.  cr.-th.,  Crico-thyroides  muscle  ;  N.  lar.  sup  v  ,  Superior 
laryngeal  nerve  ;  R.  L,  Internal  branch  ;  R.  E.,  External  branch  ;  N.  L.  R.  V.,  Recurrent  laryn- 
geal nerve  ;  R.  L  N.  L.  R.,  Internal  branch  of  the  recurrent  nerve  ;  R.  E.  N.  L  R..  External 
branch  of  the  recurrent  laryngeal  nerve. 


inserted  into  it.  It  consists  of  two  fasciculi  —  an  upper  and  a 
lower.  The  lower  and  larger  portion  is  inserted  into  the  ante- 
rior angle  and  the  anterior  surface  of  tiie  arytenoid  ;  the  upper 
is  inserted  into  the  upper  part  of  the  anterior  surface  and  the 
anterior  border  of  the  arytenoid.  Its  nerve  comes  from  the 
inferior  laryngeal  (Fig.  100). 

This  muscle  relaxes  the  vocal  cord.     More  than  this,  it  puts 


M.    THYO-ARYTENOIDEUS.  265 

the  lip  of  the  glottis  in  the  vocalizing  position  ;  in  this  position 
the  margins  of  the  glottis  are  parallel,  and  the  chink  is  reduced 
to  the  breadth  of  a  shilling. 

The  following  table  shows  the  action  of  the  several  muscles 
which  act  upon  the  glottis; — - 

Crico-thyroidei, Stretch  the  vocal  bands. 

Thyroarytenoidei,       ....  Relax  the  vocal  bands,  and  place  them 

in  the  vocalizing  position. 
Crico-arytenoidei  postici,     ,     .  Dilate  the  glottis. 
Crico-arytenoidei  laterales, .     .  Draw  together  the  arytenoid)    ,         ■ 

cartilages  [  close  the 

Arytenoideus, Ditto  ditto         ditto  )     g'°"'^- 

Aryteno-epiglottidei,  .     .     .     .  Contract  the  upper  opening  of  the  larynx. 

The  epiglottis  is  connected  by  muscles  with  the  arytenoid 
and  thyroid  cartilages  :  they  are  the  thyro-epiglottideus,  the 
aryteno-epiglottideus  superior  and  inferior. 

The  thyro-epiglottidetis  is  a  thin  muscle,  arising  from  the 
angle  of  the  thyroid  cartilage  just  above  the  thyro-arytenoideus, 
and  is  inserted  by  diverging  fibres  into  the  border  of  the  epi- 
glottis and  into  the  aryteno-epiglottic  fold. 

The  aryteno-epiglottideiis  superior  passes  as  thin  muscular 
fibres  from  the  tip  of  the  arytenoid  cartilage  to  the  mucous 
membrane  attached  to  the  side  of  the  epiglottis. 

The  aryteno-epiglottideus  inferior,  separated  from  the  preced- 
ing by  a  distant  interval,  arises  from  the  anterior  surface  of  the 
arytenoid  cartilage,  and  is  inserted  into  the  upper  and  inner  part 
of  the  epiglottis.  This  muscle  is  also  called  the  eovipressor 
saeeuli  laryngis  of  Hilton.* 

The  blood-vessels  of  the  laryjix  are  derived  from  the  superior 
and  inferior  thyroid  arteries.  The  laryngeal  branch  of  the 
superior  thyroid  passes  through  the  thyro-hyoid  membrane  with 
the  corresponding  nerve,  and  divides  into  branches,  which  supply 
the  muscles  and  the  mucous  membrane.  The  laryngeal  branches 
of  the  inferior  thyroid  ascend  behind  the  cricoid  cartilage.  A 
constant  little  artery  passes  through  the  crico-thyroid  membrane. 

The  nerves  of  the  larynx  are  the  superior  and  inferior  {recur- 
rent) laryngeal  branches  of  the  pneumogastric.     (Fig.  100.) 

The  superior  laryngeal^  having  passed  through  the  thyro-hyoid 
membrane,  divides  into  branches,  distributed  to  the  mucous 
membrane  of  the  larynx.      Its  filaments  spread  out  in  various 

*  T\ie  triticeoglossus  is  a  small  muscle  frequently  present;  it  arises  from  the 
corpus  triticeum,  and  passing  forwards  and  upwards  joins  the  cerato-glossus  to  be 
inserted  into  the  tongue. 


266  DISSECTION    OF    THE    TONGUE. 

directions  :  some  to  the  anterior  and  posterior  surfaces  of  the 
epiglottis,  and  to  the  aryteno-epiglottidean  folds,  others  to  the 
interior  of  the  larynx  and  the  vocal  bands  and  membranes.  A 
constant  filament  descends  behind  the  ala  of  the  thyroid  cartilage, 
and  communicates  with  the  inferior  laryngeal,  and  another  com- 
munication with  the  same  nerve  is  found  behind  the  larynx 
beneath  the  pharyngeal  mucous  membrane.  Its  external  laryn- 
geal branch  supplies  the  crico-thyroid  muscle. 

The  i7iferior  (or  recurrent)  laryngeal  nerve  enters  the  larynx 
beneath  the  inferior  constrictor,  and  ascends  behind  the  joint 
between  the  thyroid  and  cricoid  cartilages.  It  supplies  all  the 
intrinsic  muscles  of  the  larynx  except  the  crico-thyroid.  If  the 
recurrent  nerve  be  divided  or  in  any  way  injured,  the  muscles 
moving  the  glottis  become  paralyzed,  but  its  sensibility  remains 
unimpaired.  When  the  nerve  is  compressed  by  a  tumor  —  for 
instance,  an  aneurism  of  the  arch  of  the  aorta  —  the  voice  is 
changed  to  a  whisper,  or  even  lost. 

Difference  between  the  Male  and  the  Female  Larynx. 
—  Until  the  approach  of  puberty,  there  is  no  great  difference 
in  the  relative  size  of  the  male  and  female  larynx.  The  larynx 
of  the  male,  within  two  years  after  this  time,  becomes  nearly 
doubled  in  size ;  that  of  the  female  grows,  but  to  a  less  extent. 

The  larynx  of  the  adult  male  is  in  all  proportions  about  one- 
third  larger  than  that  of  the  adult  female. 

The  alae  of  the  thyroid  cartilage  form  a  more  acute  angle  in 
the  male;  hence  the  greater  projection  of  the  pomum  Adami 
and  the  greater  length  of  the  vocal  cords  in  the  male. 

The  average  length  of  the  vocal  bands  is  in  the   j  ^f^^.^^  ~%  °f  ^'a    \f  ^  {^f  Z"m\ 

„,,  ,       ,u     c  .u      1   .^-    •    ■     .1  \  Male  nearly      "     "       [24  vim.) 

1  he  average  length  of  the  glottis  is  in  the  .     .      j  ^^^^^^  ^  l^     ..     ..       [^^  ^^^J^ 

The  size  of  the  larynx  does  not  necessarily  follow  the  pro- 
portions of  the  general  stature  ;  it  may  be  as  large  in  a  little 
person  as  in  a  tall  one ;  this  corresponds  with  what  we  know  of 
the  voice. 

DISSECTION    OF   THE   TONGUE. 

The  tongue  is  a  complex  muscular  organ,  subservient  to  taste,  speech,  suction, 
masticatien,  and  deglutition.  It  is  situated  in  the  space  formed  by  the  lower  den- 
tal arch  ;  its  upper  surface  is  convex  and  free,  as  is  also  its  anterior  part  or  tip, 
which  lies  behind  the  lower  incisor  teeth;  its  posterior  and  inferior  part  is  con- 
nected to  the  OS  hyoides  by  the  hyo-glossi,  to  the  styloid  process  of  the  temporal 


PAPILL/E    OF    THE    TONGUE. 


267 


bone  by  the  stylo  glossi,  and  to  the  symphysis  of  the  mandible  by  the  genio-hyo- 
glossi  muscles. 

The  upper  surface  or  (/crj/^///  is  convex,  and  slopes  on  all  sides  from  the  centre; 
it  is  divided  into  two  symmetrical  halves  by  a  median  groove  —  raphe — running 
along  the  middle,  and  teiminates  posteriorly  in  a  depression  —  \.\\e  foramen  cacum 

—  into  which  open  several  mucous  glands.  The  posterior  third  of  the  dorsum  is 
comparatively  smooth ;  the  anterior  two-thirds  is  rough,  and  covered  with  small 
eminences  called  papilhc. 

Mucous  Membrane.  —  The  surface  of  the  tongue  is  covered  with  mucous 
membrane,  which  is  composed  of  structures  similar  to  those  of  the  skin  generally 

—  that  is  to  say,  it  consists  of  a  cutis  vera  with  numerous  elevations  called  papillae, 
and  of  a  thick  layer  of  squamous  epithelium.  The  cutis  is  much  thinner  than  that 
of  the  skin  of  the  body,  and  affords  insertion  to  some  muscular  fibres  of  the 
tongue. 

The  mucous  membrane  on  the  under  aspect  of  the 
tongue  is  smooth  and  comparatively  thin,  and,  in  the 
middle  line  in  front,  forms  a  fold  —  ihefranum  lingica 

—  which  connects  it  to  the  mucous  membrane  of  the 
floor  of  the  mouth.  On  each  side  of  the  frasnum  are 
the  elevated  orifices  of  the  submandibular  ducts  ;  and 
further  back,  in  the  furrow  between  the  tongue  and 
gums,  are  the  openings  of  the  sublingual  ducts.  Lat- 
erally, the  mucous  membrane  is  reflected  from  the 
under  part  of  the  tongue  to  the  mandible,  and  forms 
the  floor  of  the  mouth. 

From  the  posterior  part  of  the  tongue  the  mucous 
membrane  passes  to  the  soft  palate  on  each  side, 
forming  the  folds  termed  ihe  anterior  palatine  arches, 
which  enclose  the  palato-glossi ;  there  are  also  three 
folds  to  the  epiglottis,  termed  \.\\e  glosso-epiglottic,  two 
lateral  and  one  median,  the  latter  enclosing  a  layer 
of  elastic  tissue  called  the  glosso  epiglottic  ligament. 
This  ligament  raises  the  epiglottis  when  the  tongue 
is  protruded  from  the  mouth ;  hence  the  rule  of 
never  pulling  the  tongue  forwards  when  passing  a 
tube  into  the  oesophagus,  otherwise  the  tube  might 
pass  into  the  larynx. 

Papillae  of  the  Tongue.  —  The  anterior  two- 
thirds  of  the  tongue  is  studded  with  numerous  small 
eminences  called  papilhe  ;  these,  according  to  their 
size  and  form,  are  distinguished  into  three  kinds,  viz., 
papilhe  circicmvallatce,  papilla  fungiformes,  and 
papilUr  filiformes  (Fig,    loi). 

The  papilliE  circuinvallatce  vary  in  number  from  eight  to  twelve,  and  are  arranged 
at  the  back  of  the  tongue  in  two  rows,  which  converge  like  the  branches  of  the 
letter  V,  with  the  apex  backwards,  towards  the  foramen  ca;cum.  Each  of  these 
papillae  is  circular,  from  the  s'sth  to  iVth  of  an  inch  (.5  mm.  to  i  mm.)  wide,  and 
slightly  broader  above  than  below.  Each  is  surrounded  by  a  circular  fossa,  which 
itself  is  bounded  by  an  elevated  ring  (vallum). 

The  papillcz  fungiformes,  smaller  and  more  numerous  than  the  circumvallatce, 
are  scattered  chiefly  over  the  sides  and  tip  of  the  tongue,  and  sparingly  over  its 
upper  surface.  They  vary  in  shape,  some  being  cylindrical,  others  having  rounded 
heads  like  mushrooms :  whence  their  name.  Near  the  apex  of  the  tongue  they 
may  be  distinguished  during  life  from  the  other  papilla;  by  their  redder  color.  In 
scarlatina,  and  some  exanthematous  fevers,  these  papillae  become  elongated,  and 
of  a  bright  red  color;  as  the  fever  subsides,  their  points  acquire  a  brownish  tint, 
giving  rise  to  what  is  called  the  strawberry  tongue. 


Fig.  ioi.  —  Upper  Surface 
OF  THE  Tongue,  with  the 
Fauces  and  Tonsils. 

1.  Papillae   circumvallatae. 

2.  Papillae  fungiformes. 


268  MUSCULAR    FIBRES    OF    THE    TONGUE. 

T\\&  papilla: filiformes  {coniccc)  are  the  smallest  and  most  numerous.  They  are 
so  closely  aggregated  that  they  give  the  tongue  a  velvet-like  appearance.  Their 
points  are  directed  backwards,  so  that  the  tongue  feels  smooth  if  the  finger 
be  passed  over  it  from  apex  to  base,  but  rough  if  in  the  opposite  direction. 
These  papilla;  consist  of  small  conical  processes  arranged  for  the  most  part  in  a 
series  of  lines  running  parallel  to  the  two  rows  of  the  papillae  circumvallatae.  Each 
papilla  is  covered  with  a  thick  layer  of  epithelium,  which  is  prolonged  into  a  num- 
ber of  free  hair-like  processes. 

The  papillae  are  covered  with  one  or  more  layers  of  squamous  epithelium. 
That  which  covers  the  filiform  is  superimposed  so  thickly  as  to  give  it  sometimes 
the  appearance  of  a  brush  when  seen  under  the  microscope.  The  various  kinds  of 
fur  on  the  tongue  consist  of  thick  and  sodden  epithelium. 

Glands.  —  Numerous  small  racemose  and  acino-tubular  glands,  luigtml  glands, 
are  found  in  the  submucous  tissue  at  the  root  of  the  tongue.  They  are  similar  in 
structure  and  secretion  to  the  tonsilar  and  palatine  glands,  so  that  there  is  a 
complete  ring  of  glands  round  the  isthmus  faucium.  Small  round  orifices  upon 
their  surface  indicate  the  termination  of  their  ducts.  Other  mucous  glands,  with 
ducts  from  one-quarter  to  half  an  inch  long,  are  situated  in  the  muscular  substance 
of  the  tongue. 

Lymphoid  Tissue.  —  A  considerable  amount  of  lymphoid  tissue  is  situated  at 
the  back  of  the  tongue,  which  in  some  parts  is  collected  into  definite  masses 
called  follicles.  Small  depressions  also  occur  in  this  situation,  whose  walls  are 
studded  with  lymphoid  tissue,  and  into  which  some  of  the  mucous  glands  open. 

Glands-beneath  the  Apex  of  the  Tongue.  —  On  the  inner  surface  of  the  apex 
of  the  tongue  is  placed,  on  either  side,  a  group  of  glands  presumed  to  be  salivary. 
Considering  each  group  as  one  gland,  observe  that  it  is  oblong,  with  the  long 
diameter  from  /j  to  |  of  an  inch  (/j-  to  21  mvi.),  parallel  with  the  axis  of  the  tongue. 
It  lies  near  the  mesial  line,  a  little  below  the  ranine  artery,  on  the  outer  side  of 
the  branches  of  the  gustatory  nerve,  under  some  of  the  fibres  of  the  stylo-glossus. 
Four  or  five  ducts  proceed  from  each  group,  and  terminate  by  separate  orifices  on 
the  under  surface  of  the  tongue. 

Muscular  Fibres  of  the  Tongue.  — The  substance  of  the  tongue  is  composed 
of  muscular  fibres  and  of  a  small  quantity  of  fat.  The  extri^isic  muscles  of  the 
tongue  have  been  described  in  the  dissection  of  the  submandibular  region  (p.  116). 
"We  have  now  to  examine  its  intrinsic  muscles.  For  this  purpose  the  mucous 
membrane  must  be  removed  from  the  dorsum  of  the  tongue.  On  dissection  it  will 
be  found  that  the  great  bulk  of  the  organ  consists  of  fibres  which  proceed  in  a 
longitudinal  direction,  constituting  the  litiguales  muscles. 

The  S2iperficial  lingualis  runs  longitudinally  beneath  the  mucous  membrane  of 
the  dorsum ;  its  fibres  are  attached  posteriorly  to  the  hyoid  bone  and  run  forwards 
to  the  front  and  margin  of  the  tongue.  Posteriorly  the  muscle  is  thin  and  is 
covered  by  the  fibres  of  the  palato-glossus  and  hyo-glossus. 

The  inferior  lingualis  is  larger  than  the  preceding,  and  is  situated  on  the  under 
aspect  of  the  tongue  between  the  genio- hyo-glossus  and  the  hyo-glossus.  It  may 
be  readily  expo.sed  by  dissecting  the  under  surface  of  the  tongue  immediately  on 
the  outer  aspect  of  the  genio-hyo-glossus.  It  arises  posterioriy  from  the  hyoid 
bone  and  the  substance  of  the  tongue,  and  its  fibres  pass  forwards  to  the  tip  of  the 
tongue  after  being  reinforced  by  fibres  from  the  stylo-glossus.  On  its  under  aspect 
it  is  in  relation  with  the  ranine  artery. 

The  trans^'crse  fibres  form  a  considerable  part  of  the  thickness  of  the  tongue 
and  arise  from  the  fibrous  septum.  They  pass  outwards  between  the  superficial 
and  inferior  linguales,  ascending  as  they  near  the  sides  of  the  tongue,  where  the 
fibres  become  continuous  with  those  of  the  palato-glossus.  A  consiclerable  amount 
of  fat  is  found  among  these  fibres. 

The  vertical  fibres  run  in  a  curved  direction,  descending  from  the  dorsum  to  the 
under  aspect  of  the  tongue,  with  the  concavity  outwards.  They  interlace  with  the 
transverse  fibres  and  with  the  genio-hyo-glossus. 


THE    MAXILLARY    NERVE.  269 

Oil  tracing  the  genio  hyo-glossi  into  the  tongue,  we  find  that  some  of  their  fibres 
ascend  directly  to  the  surface  ;  others  cross  in  the  middle  line,  intersect  the  longi- 
tudinal fibres,  and  finally  terminate  Uipon  the  sides  of  the  tongue.  Lastly,  the 
fibres  of  the  styloglossi  should  be  traced  along  the  side  of  the  tongue  to  the  apex. 

Fibrous  Septum  of  the  Tongue.  —  The  Jibrotis  septum  of  the  tongue  is  a 
vertical  plane  of  fibrous  tissue  which  extends,  in  the  mesial  line,  from  the  base  to 
the  apex.  It  is  thick  posteriorly,  where  it  is  connected  behind  with  the  hyoid 
bone  and  is  lost  in  front  between  the  muscles.  In  it  is  sometimes  found  a  piece 
of  fibro-cartilage,  called  nucleus  fibrosus  lingua:,  a  representative  of  the  lingual 
bone  in  some  of  the  lower  animals. 

The  arteries  supplying  the  tongue  are  the  dorsal  and  ranine  branches  of  the 
lingual  arteries.  It  is  important  to  bear  in  mind  that  the  arteries  do  not  anasto- 
mose across  the  middle  line,  and  only  very  slightly  at  the  apex,  so  that  it  is  pos- 
sible to  cut  along  the  septum  of  the  tongue  from  the  apex  to  the  base  viith  very 
little  haemorrhage,  —  a  fact  of  much  importance  in  the  removal  of  the  tongue  or 
cancer  of  that  organ. 

The  nerves  to  the  tongue  should  now  be  followed  to  their  termination.  The 
hpyoglossal  supplies  with  motor  power  all  the  muscles.  The  gustatory  or  lingual 
branch  of  the  mandibular  division  of  the  fifth  is  distributed  to  the  mucous  mem- 
brane and  papillae  of  the  apex  and  sides  of  tongue,  supplying  the  anterior  two- 
thirds  with  common  sensations.  Upon  this  nerve  depends  the  sensation  of  all 
ordinary  impressions,  such  as  that  of  hardness,  softness,  heat,  cold,  and  the  like. 

The  glosso-pkaryngeal  nerve  supplies  the  mucous  membrane  at  the  back  and 
the  sides  of  the  tongue,  and  the  papillae  circumvallatae.  Under  the  microscope 
small  ganglia  may  be  distinguished  on  the  terminal  fibres  of  this  nerve. 

DISSECTION    OF   THE    MAXILLARY   NERVE. 

To  trace  thi.s  nerve  and  its  branches  we  must  remove  the 
outer  wall  of  the  orbit  as  far  as  the  foramen  rotundum,  so  as  to 
expose  the  spheno-maxillary  fossa. 

The  maxillary  nerve  is  a  sensory  nerve,  and  is  the  second 
division  of  the  fifth  cranial  nerve.  Proceeding  from  the  Gasse- 
rian  ganglion  (Fig.  102),  it  leaves  the  skull  through  the  foramen 
rotundum,  and  passes  horizontally  forwards  across  the  spheno- 
maxillary fossa.  It  then  passes  into  the  orbit  through  the 
spheno-maxillary  fissure,  enters  the  infra-orbital  canal  with  the 
corresponding  artery,  and  finally  emerges  upon  the  face,  through 
the  infra-orbital  foramen,  beneath  the  levator  labii  superioris, 
where  it  divides  into  a  number  of  spreading  branches,  distrib- 
uted to  the  lower  eyelid,  the  nose,  and  the  upper  lip.  The 
branches  given  off  are  :  — 

1.  Within  the  skull. 

a.  A  recurrent  branch,  to  the  dura  and  middle  meningeal  artery,  is  given  off 
near  the  Gasserian  ganglion. 

2.  In  the  spheno-maxillary  fossa. 

b.  The  orbital  branch  already  described  (p.  77). 

c.  Two  spheno palatine  branches  which  descend  to  the  sphenopalatine  ganglion 
(Meckel's),  situated  in  the  spheno-maxillary  fossa  (Fig.  102). 


270 


THE    MAXILLARY    NERVE. 


d.  The  denial  hrancAes  are  three  in  number :  the  two  posterior  are  given  off 
immediately  belore  the  nerve  enters  the  infra-orbital  canal,  and  descends  along 
the  tuberosity  of  the  maxillary  bone  ;  the  anterior  is  given  off  in  the  intra-orbital 
canal.  Tha  posterior  branch  divides  into  two  branches,  which  send  small  filaments 
to  the  gums  and  the  mucous  membrane  of  cheek,  and  then  run  in  bony  canals  in 
company  with  small  arteries  to  supply  the  molar  teeth  and  the  antium;  the  fiiid- 
dle  branch  passes  down  in  a  special  canal  in  front  of  the  antrum  to  be  distributed 
to  the  bicu-pid  teeth;  the  anterior  bj-anch,  ^^^^  largest,  is  given  cff  before  the 
ner^'e  emerges  from  the  infra-orbital  foramen,  and  enters  the  caral  in  the  front 
wall  of  the  antrum ;  it  divides  into  denial  branches  for  the  supply  of  the  canine 
and  incisor  teeth,  and  into  a  nasal  branch  for  the  mucous  mtmbiane  of  the  floor 
of  the  nasal  fossa.  The  anterior  branch  while  in  its  bony  canal  gives  off  some 
filaments,  which  join  with  the  posterior  dental  branches,  and  above  the  canine 
fossa  it  also  forms  a  communication  with  a  nasal  branch  from  the  f-pheno  palatine 
ganglion  to  fonn  Van  gajiglion  of  Boehdalek. 

e.  The  terminal  branch  of  the  maxillary  nerve  is  called  the  injra-orbiial,  which 
divides  on  the  face  into  palpebral,  nasal,  and  labial  branches.  These  have  been 
already  dissected  and  described  (p.  62). 


Trunk  of  the 
fifth  nerve. 

BB 

B 

■1 

Gasserian 
ganglion. 

B|.4" 

BH 

^^a 

Facial  n. 

Hh^I 

R 

nH 

Chorda  tym- 
pani. 

^^n 

HH 

.Siibmandihu- 
lar    gangli- 
on. 

j^B 

1 

B 

^H 

Frontal,  lach- 
rymal and 
nasal  nn. 

Orbital 
branch. 

Infra-orbital 


Anterior  den- 
tal n. 

Naso-pala- 
tine  n. 

Palatine  n. 


r7Ustatory  n. 


Fig.  102.  —  Diagram  of  the  Maxillary  Nervb. 
I.  Spheno-palatine  ganglion.     2.  Otic  ganglion. 

Dissection.  —  At  this  sta.oe  the  student  should  make  the 
dissection  to  expose  the  spheno-palatine  ganglion  and  its 
branches.  To  do  this  it  is  necessary  to  saw  through  the  skull 
rather  on  one  side  of  its  middle  line,  so  as  to  expose  the  cavity 
of  the  nose.  Search  must  now  be  made  for  the  spheno-palatine 
foramen  (just  external  to  which  is  the  spheno-palatine  ganglion), 
which  is  situated  immediatelyabove  the  posterior  extremity  of 
the  middle  turbinated  bone.  Remove  the  mucous  membrane 
at  this  point,  when  the  terminal  branch  of  the  internal  maxillary 
artery,  which  comes  through  this  foramen  into  the  nose,  may 


SPHENO-PALATINE    GANGLION. 


271 


be  readily  made  out.  The  student  should  next  cut  away  the 
thin  plate  of  bone  which  forms  the  inner  boundary  of  the  pos- 
terior palatine  canal.  Then,  by  tracing  upwards  the  branches 
contained  within  the  canal,  he  will  find  the  ganglion. 

Spheno-palatine  Ganglion. —  This  ganglion  is  called,  after 
its  discoverer,  Meckel's  ganglion.  It  is  the  largest  of  the  gan- 
glia in  connection  with  the  branches  of  the  fifth  cerebral  nerve, 
is  triangular,  convex  on  its  outer  surface,  of  reddish-gray  color, 
about  one-fifth  of  an  inch  (5  ;//;;/.)  in  diameter,  and  is  placed 
immediately  below  the  maxillary  nerve,  as  it  crosses  the  spheno- 


Anterior  dental. 


Maxillary  nerve. 


Orbital  branch. 


Maxillary  nerve. 


Meckel's  ganglion. 


Posterior  dental 


Loop  formed  by  middle  and  anterior  dental  nerves. 

Fig.  103. — The  Maxillary  Nerve  seen  fro.m  without.     (Eeaunis.) 

maxillary  fossa.  Like  other  ganglia,  it  has  three  roots  —  a 
sensory,  from  the  maxillary  ;  a  motor,  from  the  great  petrosal 
branch  of  the  fascia  ;  and  a  sympathetic,  from  the  carotid  plexus. 
Its  branches  pass  npivards  to  the  orbit,  dowtiwards  to  the 
palate,  imvards  to  the  nose,  and  backwards  to  the  pharynx,  as 
follows  :  — 

a.  Ascending  branches. — These  are  very  small,  and  run  through  the  spheno- 
maxillary fissure  to  be  distributed  to  the  periosteum  of  the  orbit.* 

*  Anatomists  describe  several  branches  ascending  from  the  ganglion ;  one  to 
join  the  sixth  nerve  (Bock) ;  another  to  join  the  ophthalmic  ganglion  (Tiedemann) ; 
and,  lastly,  some  to  join  the  optic  nerve  through  the  ciliary  branches  (Hirzel). 


2/2  OTIC    GANGLION. 

b.  Descending  branches. —  To  see  these  the  mucous  membrane  must  be  removed 
from  the  back  part  of  the  nose ;  we  shall  then  be  able  to  trace  the  nerves  through 
their  bony  canals.  Their  course  is  indicated  by  their  accompanying  arteries. 
They  descend  through  the  palatine  canals,  and  are  three  in  number.  The  ante- 
rior pa  Uiti)ie  nerve,  the  laigest,  descends  through  the  posterior  palatine  canal  to 
the  roof  of  the  moulh,  and  then  divides  into  branches,  which  run  in  grooves  in  the 
hard  palate  nearly  to  the  gums  of  the  incisor  teeth,  where  it  communicates  with 
the  nasopalatine  nerve.  Within  its  canal  it  sends  two  infej-ior  nasal  bratiches 
which  enter  the  nose  through  foramina  in  the  palate  bone  to  supply  the  mem- 
brane on  the  middle  and  lower  spongy  bones.  The  posterior  or  smaller  palatine 
descends  in  the  same  canal  with  the  anterior,  or  in  a  smaller  one  of  its  own,  and 
supplies  the  mucous  membrane  of  the  soft  palate,  the  tonsil,  and  (according  to 
Meckel)  the  levator  palati  muscle.*  The  external  palatine  may  be  traced  in  a 
special  canal  down  to  the  soft  palate,  where  it  terminates  in  branches  to  the  uvula, 
the  palate,  and  tonsil.  The  two  last  branches  communicate  with  the  tonsilar  fila- 
ments of  the  giosso-pharyngeal  to  form  the  tonstlar  plextcs  of  nerves. 

c.  Internal  branches.  —  These,  three  or  four  in  number,  pass  through  the 
sphenopalatine  foramen  to  the  mucous  membrane  of  the  nose.  To  see  them 
clearly  the  parts  should  have  been  steeped  in  dilute  nitric  acid;  afterwards,  when 
well  washed,  these  minute  filaments  may  be  recognized  beneath  the  mucous  mem- 
brane covering  the  turbinated  bones.  The  upper  nasal  branches,  four  or  five  in 
number,  pass  inwards,  and  are  distributed  on  the  two  upper  spongy  bones,  the 
upper  and  back  part  of  the  septum,  and  the  posterior  ethmoidal  cells.  The  naso- 
palatine (nerve  of  Contunnius)  traverses  the  roof  of  the  nose,  distributes  branches 
to  the  back  part  of  the  septum  narium,  and  then  proceeds  obliquely  forwards, 
along  the  septum,  to  the  foramen  incisivum,  through  which  it  passes,  and  finally 
terminates  in  the  palate  behind  the  incisor  teeth,  communicating  here  with  the 
anterior  palatine  nerve. 

d.  Posterior  branches.  —  'T\^^  pharyngeal  7ierve  (pterygo-palatine),  very  small, 
comes  off  from  the  back  of  the  ganglion,  and,  after  passing  through  the  pterygo- 
palatine canal  with  its  corresponding  artery,  supplies  the  mucous  membrane  of  the 
back  of  the  pharynx  and  the  Eustachian  tube.  The  Vidian  nerve  is  the  principal 
branch.  It  proceeds  backwards  from  the  posterior  part  of  the  ganglion,  through 
the  Vidian  canal,  where  it  distributes  small  branches  to  the  back  part  of  the  roof 
of  the  nose  and  septum.  It  then  traverses  the  fibro-cartilage  of  the  foramen 
lacerum  medium,  and  divides  into  two  branches.  Of  these  two  branches  one,  the 
larger  —  the  carotid — joins  the  sympathetic  plexus  on  the  outer  side  of  the  in- 
ternal carotid  artery;  the  o^^a^x  —  \.\i&  great  petrosal — enters  the  cranium  and  nins 
beneath  the  Gasserian  ganglion  and  the  dura  in  a  small  groove  on  the  anterior 
surface  of  the  petrous  bone ;  it  then  enters  the  hiatus  Fallopii,  and  joins  the  facial 
nerve  in  the  aqujeductus  Fallopii. 

It  would  seem  to  be  more  in  accordance  with  modern  views  to  regard  the 
Vidian  nerve,  not  as  dividing  to  foim  the  carotid  and  great  supei-ficial  petrosal 
branches,  but  rather  as  formed  by  the  junction  of  these  branches.  In  this  view 
the  Vidian  runs,  not  from,  but  to,  the  spheno-palatine  ganglion. 

Otic  Ganglion.  —  The  otic  ganglion  (Arnold's)  is  situated  on  the  inner  side  of 
the  mandibular  division  of  the  fifth  nerve,  immediately  below  its  exit  through  the 
foramen  ovale  (Fig.  102,  p.  270).  It  is  oval,  of  reddish-gray  color,  and  always  small. 
Its  inner  surface  is  in  contact  with  the  circumflexus  (or  tensor)  palati  muscle  and 
the  cartilage  of  the  Eustachian  tube;  behi7id  it  is  the  middle  meningeal  artei^  ; 

*  According  to  Ix)nget  {Anal,  et  Physiol,  dti  Systtme  Nerveux,  Paris,  1842) 
the  posterior  palatine  nerve  supplies  the  levator  palati  and  the  azygos  uvulae  with 
motor  power.  In  this  view  of  the  subject  the  nerve  is  considered  to  be  the  con- 
tinuation or  terminal  branch  of  the  motor  root  of  the  ganglion;  that,  namely, 
derived  from  the  facial.  This  opinion  is  sup])orted  by  cases  in  which  the  uvula  is 
slated  to  have  been  drawn  on  one  side  in  consequence  of  paralysis  of  the  oiiposite 
facial  nerve. 


OTIC    GANGLION. 


273 


exterually  it  is  in  relation  with  the  mandibular  nerve,  where  the  motor  root  joins 
the  sensory  root. 

This  gangUon  has  branches  of  connection  with  other  nerves  ;  namely,  a  sciisoiy 
from  the  auriculotemporal  nerve;  a  motor  from  the  branch  of  the  mandibular, 
which  goes  to  the  internal  pterygoid  muscle;  and  a  sympathetic  from  the  ple.xus 
around  the  arteria  meningea  media.  It  communicates  also  with  the  facial  and  the 
glosso  pharyngeal  nerves  by  the  lesser  petrosal  nerve.     This  branch  passes  back- 


N.  to  great  petrosal. 
N.  to  lesser  petrosal. 

N.  to  Eustachian  tube. 
Ns.  to  carotid  plexus. 

Chorda  tympani. 

N.  to  stylo-hj'oid. 

N.  to  digastric. 
Petrous  ganglion. 

Carotid  plexus. 

r.ranch  to  pharyngeal 
plexus. 

Lingual  branch. 

Ga-igliim  of  the  trunk. 


Pharyngeal  n. 


Superior  lar5mgeal. 


GanRliform  enlarge- 
ment. 
N.  to  fenestra  ovalis. 
N.  to  fenestra  rotunda. 


Tympanic  n. 

Auricular  n. 
Glosso-pharjTigeal  n. 
Jugular  ganglion  of  do. 

Pneumogastric. 
Ganglion  of  root. 

Spinal  accessory. 


Hypoglossal. 


Supr.  cervical  ganglion 
ist  cervical  n. 

Br.  to  ganglion  of 
trunk. 

2nd  cervical  n. 


Fig.  104.  —  Diagram  of  the  Communications  of  the  Facial,  Glosso-Pharyngeal,  Pneu- 
MOGASTJdc,  Spinal  Accessory,  Hypoglossal,  Sympathetic,  and  the  Two  Upper 
Cervical  Nerves. 


Great  petrosal  nerve.     2.   Lesser  petrosal  nerve.     3.  External  petrosal  nerve.     4. 
pedius  muscle.     5.  Spheno-palatine  ganglion.    6.  Otic  ganglion. 


Nerve  to  Sta- 


wards,  either  through  the  foramen  oval  or  the  foramen  spinosum,  or  through  a 
small  hole  between  them,  and  runs  beneath  the  dura  in  a  minute  groove  on  the 
petrous  bone,  external  to  that  for  the  great  petrosal  nerve.  Here  it  divides  into 
two  filaments,  one  of  which  joins  the  facial  nerve  in  the  aquaeductus  Fallopii ;  the 
other  joins  the  tympanic  branch  of  the  glossopharyngeal.  These  nerves  are 
difficult  to  trace,  not  only  on  account  of  their  minuteness,  but  because  they  fre- 
quently run  in  canals  m  the  temporal  bone. 


274  NERVES    AT    THE    BASE    OF    THE    SKULL. 

The  otic  ganglion  sends  a  branch  forwards  to  the  tensor  palati,  and  one  back- 
wards to  the  tensor  tympani,  on  the  outer  side  of  the  Eustachian  tube. 


DISSECTION  OF  THE  NINTH,  TENTH,  AND  ELEVENTH  CRANIAL 
NERVES  AT  THE  BASE  OF  THE  SKULL. 

In  this  dissection  we  propose  to  examine  the  glosso-pharyngeal,  pneumogastric, 
and  spinal  accessory  nerves  in  the  jugular  fossa,  and  the  ganglia  and  nerves  be- 
longing to  them  in  this  part  of  their  course.  These  are  difficult  to  trace,  and 
cannot  be  followed  unless  the  nerves  have  been  previously  hardened  by  spirit  and 
the  bones  softened  in  acid.  The  next  thing  to  be  done  is  to  remove  the  outer 
wall  of  the  jugular  fossa. 

Glosso-pharyngeal  Nerve,  or  Ninth  Nerve.  — This  nerve  emerges  from  the 
cranium  through  a  separate  tube  of  dura,  in  front  of  that  for  the  tenth  and 
eleventh  cranial  nerves.  Looking  at  it  from  the  interior  of  the  skull,  we  notice 
that  it  is  situated  in  front,  and  rather  to  the  inner  side  of  the  jugular  fossa,  where 
it  lies  in  a  groove. 

In  its  passage  through  the  foramen,  the  nerve  presents  two  enlargements, 
termed  i\\&  jzigular  and  the  pet7-ons  ganglion. 

The  Jugular  ganglion  {ganglion  of  Ehrenritter')  is  found  upon  the  nerve  im- 
mediately after  its  entrance  into  the  canal  of  the  dura,  and  averages  about  the 
one  twentieth  of  an  inch  [1.2^  nun?)  in  length  and  breadth.  It  is  situated  on  the 
outer  side  of  the  nerve,  and  does  not  implicate  all  its  fibres.  According  to  our 
obsei'vation,  this  ganglion  is  not  infrequently  absent  (Pig.  97). 

The  petrous  ganglion  {ganglion  of  Andersck)  is  lodged  in  a  groove  in  the 
lower  part  of  the  jugular  fossa.  It  is  oval,  about  a  quarter  of  an  inch  {6  mm.) 
long,  and  involves  all  the  filaments  of  the  nerve.  From  it  are  given  off  branches 
of  communication  with  other  nerves  and  the  tympanic  nerve  (Fig.  104).* 

The  communicating  branches  which  connect  this  ganglion  with  the  pneumo- 
gastric are,  one  to  its  auricular  branch,  and  a  second  to  the  ganglion  of  the  root. 

It  is  also  connected  with  the  sympathetic  by  a  small  filament  from  the  superior 
cer\'ical  ganglion.  Another  communicating  branch  pierces  the  posterior  belly  of 
the  diagastricus  to  join  the  facial  just  external  to  the  stylo-mastoid  foramen. 

The  tympanic  nerve  (Jacobson's)  ascends,  through  a  minute  canal  in  the  bony 
ridge  which  separates  the  carotid  from  the  jugular  fossa,  to  the  inner  wall  of  the 
tympanum,  grooving  the  surface  of  the  promontory,  where  it  terminates  in  six 
filaments.  Of  these,  three  are  branches  of  distribution,  and  three  of  communica- 
tion with  other  nerves.  The  branches  of  distrilmtion  are,  one  each  to  the  fenestra 
rotunda  and  the  fenestra  ovalis,  which  pass  backwards,  and  one  to  the  Eustachian 
tube,  which  is  directed  forwards.  The  branches  of  comtminicaiion  are  four  small 
filaments ;  one  or  two  traverse  a  bony  canal  in  the  anterior  wall  of  the  tympanum, 
and  arching  fonvards,  join  the  plexus  on  the  outer  side  of  the  carotid  artery; 
another,  the  small  deep  petrosal  7ierve,  runs  in  a  canal  in  the  processus  cochleari- 
formi.s,  passes  through  the  foramen  lacerum  medium  to  join  the  carotid  plexus  ;  a 
third  a.scends  in  front  of  the  fenestra  ovalis,  and,  passing  forwards,  joins  the  great 
petrosal  nerve  in  the  hiatus  Fallopii ;  the  fourth  leaves  the  front  of  the  tympanum 
under  the  name  of  the  small  superficial  petrosal  nerve,  through  a  canal,  where  it 
is  joined  by  a  filament  from  the  geniculate  ganglion  of  the  facial  nerve;  then 
passing  beneath  the  canal  for  the  tensor  tympani,  it  emerges  through  a  foramen 
on  the  anterior  surface  of  the  pars  pelrosa,  external  to  the  hiatus  Fallopii;  it  pro- 
ceeds along  the  anterior  surface  of  pars  petrosa,  and  emerges  from  the  skull 
1)etween  the  great  wing  of  the  sphenoid  and  the  petrous  bones  to  join  the  otic 
ganglion.     Thus  the  tympanic  branch  is  distributed  to  the  mucous  membrane  of 

*  This  nerve,  though  commonly  called  Jacobson's,  was  fully  described  by 
Andersch, 


FACIAL    NERVE    IN    THE    TEMPORAL    BONE.  2/5 

the  tympanum  and  the  E.istachian  tube,  and  commuiucates  with  the  sphenopala- 
tine gangUon  through  the  great  petrosal  nerve,  and  with  the  otic  ganglion  through 
the  lesser  petrosal  (Fig.  104). 

Pneumogastric  Nerve,  or  Tenth  Nerve.  —  This  nerve  leaves  the  cranium 
with  the  nervus  accessorius  through  a  common  canal  in  the  dura,  behind  that  for 
the  glosso-pharyngeal.  At  its  entrance  into  the  canal  it  is  composed  of  a  number 
of  separate  filaments,  which  are  soon  collected  into  a  single  trunk.  In  the  jugular 
foramen  the  nerve  presents  a  ganglionic  enlargement,  4  to  6  mm.  in  length,  called 
the.  oanirlion  of  the  root ;  and,  after  the  nerve  has  emerged  from  the  jugular  fora- 
men, it  presents  a  second  ganglion,  larger  than  that  of  the  root  fusiform  in 
appearance,  about  20  mm.  in  length  and  4  to  5  mm.  in  thickness  —  the  ganglion  of 
the  trunk  of  the  nerve  —  where  it  is  joined  by  the  accessory  portion  of  the  spinal 
accessory  nerve.  It  is  connected  by  filaments  with  the  sympathetic  through  the 
superior  cervical  ganglion,  with  the  petrous  ganglion  of  the  glosso-pharyngeal, 
with  the  auricular  branch  of  the  facial,  and  with  the  spinal  accessory  by  one  or 
two  branches.  It  gives  off  the  auricular  branch,*  which  is  distributed  to  the 
pinna  of  the  ear.  This  branch,  shortly  after  its  origin,  is  joined  by  a  branch  from 
the  petrous  ganghon  of  the  glosso-pharyngeal,  and,  passing  outwards  behind  the 
internal  jugular  vein,  it  enters  a  minute  foramen  in  the  jugular  fossa  near  the 
styloid  process.  It  then  proceeds  through  a  canal  in  the  bone,  crosses  the  aquoe- 
ductus  Fallopii,  where  it  communicates  with  the  facial  nerve,  and  passes  to  the 
outside  of  the  skull  through  the  fissure  between  the  mastoid  process  and  the 
meatus  auditorius  e.xternus.  It  here  divides  into  two  branches,  one  being  dis- 
tributed to  the  skin  of  the  auricle,  and  communicating  with  the  great  auricular 
nerve ;  the  other  communicating  with  the  posterior  auricular  branch  of  the  facial 
over  the  mastoid  process.  This  ganglion  also  sends  backwards  a  meningeal 
branch,  which  passes  through  the  jugular  foramen  to  be  distributed  to  the  dura 
of  the  posterior  fossa  (Fig.  104). 

The  ganglion  of  the  trunk  has  communications  with  the  hypoglossal  nerve, 
with  the  loop  formed  between  the  first  and  second  cervical  nerves,  and  with  the 
superior  cervical  ganglion  of  the  sympathetic.  It  gives  off,  as  branches  of  dis- 
tribution, the  pharyngeal  and  superior  laryngeal  nerves.  This  has  been  previously 
described  (p.  158). 

Facial  or  Seventh  Nerve  in  the  Temporal  Bone.  —  The  facial  nerve  is  con- 
tained within  the  meatus  auditorius  internus,  together  with  the  auditory  nerve. 
At  the  bottom  of  the  meatus  the  two  nerves  are  connected  by  one  or  more  fila- 
ments. The  facial  nerve  then  enters  the  aquaeductus  Fallopii.  This  is  a  tortuous 
canal  in  the  substance  of  the  temporal  bone,  and  terminates  at  the  styloid-mastoid 
foramen.  The  nerve  proceeds  from  the  meatus  auditorius  internus  for  a  short 
distance  outwards  tow-ards  the  hiatus  Fallopii,  where  it  presents  a  ganglionic  en- 
largement—  the  intumescenfia  ganglijcrmis,  or  geniculate  ganglion  —  W'here  it  is 
joined  by  several  nerves;  it  then  makes  a  sudden  bend  backwards  along  the  inner 
wall  of  the  tympanum  above  the  fenestra  ovalis,  and,  lastly,  curving  downwards 
along  the  back  of  the  tympanum,  it  leaves  the  skull  through  the  stylo-mastoid 
foramen. 

Its  branches  of  communication  in  the  temporal  bone  are:  — 
Those  in  the  meatus  auditorius  internus  — 

a.  With  the  auditory  nerve. 

Those  in  the  aqu^eductus  Fallopii  — 

b.  With  Meckel's  ganglion  through  the  large  petrosal  nerve. 

c.  With  the  otic  ganglion  through  the  small  superficial  petrosal  nerver 

d.  With  the  sympathetic  around  the  middle  meningeal  artery  through  the 
external  superficial  petrosal  nerve. 

*  Arnold's  nerve. 


2/6 


FACIAL    NERVE    IN    THE    TEMPORAL    BONE. 


Its  branches  of  distribution  are :  — 
e.    The  tympanic  branch. 
f.    The  chorda  tympani. 

a.  The  commiDiicatitig  branches  with  the  auditory  are  by  several   filaments,  in 
the  meatus  auditorius  internus. 

b.  T\ie  large  petrosal  nerve  )o\ns  the  carotid  branch  from   the  sympathetic  to 
form  the  Vidian  nei-ve,  which  joins  the  spheno-palatine  ganglion  (Fig.  105,  3). 

c.  The  sfnall  superficial  petrosal  nerz'e  passes  along  the  anterior  surface  of  the 
pars  petrosa  to  join  the  otic  ganglion  below  the  foramen  ovale  (Fig.  105,  4). 

(/.    The  external  superficial  petrosal  nej-ve  passes   from  the   geniciilate  ganglion 
to  the  sympathetic  ple.xus  around  the  middle  meningeal  artery  (Fig.  105,  5). 

e.    The  tympanic  branch  passes  through  a  foramen  in  the  base  of  the  posterior 
pyramid  to  supply  the  stapedius  and  the  laxator  tympani  (Fig.  104,  4).* 

/.    The  chorda  tympa7ii  is  given  off  from  the  facial    nerve  before  its  exit  from 

the  stylomastoid  foramen.!  It  ascends 
a  short  distance  in  a  bony  canal  at  the 
back  of  the  tympanum,  and  enters  that 
cavity  through  a  small  foraman — foramen 
chordae  posterius  —  below  and  external  to 
the  pyramid,  close  to  the  membrana  tym- 
pani. It  runs  forwards,  ensheathed  in 
mucous  membrane,  through  the  tym- 
panum, between  the  handle  of  the  malleus 
and  the  long  process  of  the  incus,  to  the 
anterior  part  of  that  cavity.  It  emerges 
through  a  small  aperture  —  foramen 
chordae  anterius  —  then  traverses  a  special 
bony  canal  —  canal  of  Huguier  —  and 
makes  its  exit  close  to  the  fissura  Glasevi. 
It  passes  downwards  and  forwards  be- 
tween the  two  pterygoid  muscles,  behind 
the  arteria  meningea  media,  the  auriculo- 
temporal and  inferior  dental  nerves,  to 
join,  at  an  acute  angle,  the  lower  border 
of  the  gustatory  nerve.  It  then  pioceeds 
in  part  to  the  submandibular  ganglion, 
and  in  part  to  the  lingualis  muscle. 


Fig.  105.  —  The  Geniculatb  Ganglion  of 
THE  Facial  Nerve,  and  its  Connec- 
tions WITH  THE  Other  Nerves.  (From 
Bidder.) 

I.  The  chorda  tympani.  2.  The  geniculate 
ganglion  of  the  facial  nerve.     3.    The  great 

fietrosal  nerve.  4.  The  lesser  petrosal  nerve 
ying  over  the  tensor  tympani.  5.  The  ex- 
ternal petrosal  nerve  communicating  with 
the  sympathetic  plexus  on  the  arteria  men- 
ingea media  (6).    7.  The  Gasserian  ganglion. 


External  to  the  stylo-mastoid 
foramen,  the  facial  nerve  com- 
municates with  the  pneumogas- 
tric,  the  glosso-pharyngeal,  the  great  auricular,  the  auriculo- 
temporal nerves,  and  with  the  carotid  plexus  ;  and  on  the  face, 
with  the  numerous  branches  of  the  three  divisions  of  the  fifth 
nerve.  Its  branches  of  distribution,  close  to  the  stylo-mastoid 
foramen,  are  the  posterior  auricular,  digastric,  and  stylo-hyoid 
branches  ;  and  on  the  face,  branches  to  all  the  facial  muscles 
and  the  platysma  myoides. 


*  This  is  often  not  muscular,  but  ligamentous  in  structure. 

t  In  the  ffjetus  this  nerve  is  given  off  outside  the  foramen,  but  subsequently 
the  bone  grows  downwards  so  as  to  enclose  more  of  the  facial  nerve,  and  witli  it 
the  chorda  tympani. 


SECOND    CERVICAL    NERVE.  2// 

Course  of  the  Internal   Carotid   through  Base   of  Skull. 

The  cervical  portion  of  the  internal  carotid  has  been  already 
described  (p.  157).  Its  subsequent  course  may  be  divided  into 
the  petrous,  cavernous,  and  cerebral  portions. 

In  the  petrous  portion,  the  artery  takes  a  very  tortuous 
course  ;  at  first  it  ascends  for  a  short  distance  ;  it  then 
curves  forwards  and  inwards  ;  and  lastly,  it  again  ascends  to 
reach  the  side  of  the  body  of  the  sphenoid.  It  is  situated 
in  front  of  the  tympanum,  from  which  it  is  separated  by  a  thin 
lamella  of  bone,  which  is  frequently  absorbed  in  advanced  age. 
It  gives  off  a  tympanic  branch  to  the  tympanum  and  membrana 
tympani. 

In  the  cavernous  portion,  the  artery  again  makes  a  series  of 
curves  :  at  first  it  ascends  forwards  on  the  side  of  the  body  of 
the  sphenoid,  and  then  curves  upwards  on  the  inner  side  of  the 
anterior  clinoid  process.  The  artery  in  this  part  of  its  course 
lies  in  the  inner  wall  of  the  cavernous  sinus,  having  the  sixth 
nerve  below  and  to  its  outer  side.  From  this  portion  are  given 
off  arteries  receptaculi  to  supply  the  conarinm  (pituitary  body) 
Gasserian  ganglion,  and  neighboring  structures  ;  the  anterior 
meningeal  or  prediiral  to  supply  the  dura ;  and  the  opJithalmic 
artery  already  described  (p.  72). 

In  the  cerebral  portion,  it  pierces  the  dura  on  the  inner  side  of 
the  anterior  clinoid  process,  and  is  surrounded  by  a  sheath 
of  the  arachnoid.  It  gives  off  the  anterior  cerebral,  the  middle 
cerebral,  the  anterior  choroid,  and  the  posterior  communicating 
artenes. 

The  internal  carotid  is  accompanied  in  the  carotid  canal  by 
the  cranial  branch  of  the  superior  cervical  ganglion  of  the  sym- 
pathetic, described  p.  163.  Its  position  on  the  inner  wall  of 
the  cavernous  sinus,  and  the  nervous  plexuses  upon  it,  are 
described  at  p.  39. 

At  this  stage  of  the  dissection  we  may  conveniently  trace  the  anterior  divisions 
of  the  two  upper  cervical  nerves. 

Suboccipital  Nerve.  —  The  anterior  division  of  the  first  cervical  or  stil>- 
occipilal  nerve  descends  in  front  of  the  transverse  process  of  the  atlas  to  form  a 
loop  with  the  ascending  branch  of  the  second  cervical  nerve.  It  lies  beneath  the 
vertebral  artery,  on  the  inner  side  of  the  rectus  capitis  lateralis,  to  which  it  gives  a 
branch ;  as  also,  one  to  the  occipito-atloid  joint,  one  to  the  rectus  capitis  anticus 
minor,  and  one  to  the  sympathetic  around  the  vertebral  artery.  From  its  loop  of 
communication  with  the  second  nerve  it  gives  filaments  of  communication  to  the 
superior  cervical  ganglion,  to  the  hypoglossal  and  pneumogastric  nerves ;  and 
muscular  branches  to  the  longus  colli  and  rectus  capitis  anticus  major. 

Second  Cervical  Nerve. — The  anterior  division  of  this  nerve  emerges  be- 
twcieii  the  arches  of  the  atlas  and  axis,  and  passes  between  the  vertebral  artery 


278  DISSECTION    OF    THE    NOSE. 

and  the  intertransverse  muscle,  in  front  of  which  it  subdivides  into  an  ascending 
branch  which  joins  the  first  cervical  nerve,  and  into  a  descending  which  joins  the 
third  cervical  nerve. 


DISSECTION   OF   THE   NOSE. 

Presuming  that  the  dissector  is  familiar  with  the  bones  composing  the  skeleton 
of  the  nose,  we  shall  now  describe :  i.  The  nasal  cartilages  ;  2.  The  general  figure 
and  arrangement  of  the  nasal  cavities  ;  3.  The  membrane  which  lines  them  ;  and 
4.    The  distribution  of  the  olfactory  nerves. 

Cartilages  of  the  Nose.  — The  framework  of  the  external  nose  is  formed  by 
five  cartilages ;  on  each  side  by  two  lateral  cartilages  ;  and  by  one  in  the  centre, 
which  completes  the  septum  between  the  nasal  fossae. 

The  lateral  cartilages  are  termed,  respectively,  upper  and  lower,  which  are  cov- 
ered externally  by  integument,  and  are  lined  internally  by  mucous  membrane.  The 
7ipfer,  triangular  in  shape,  is  connected  superiorly  to  the  margin  of  the  nasal  and 
maxillary  bones ;  anteriorly,  which  is  its  thickest  part,  to  the  cartDage  of  the  sep- 
tum ;  and,  inferiorly,  to  the  lower  cartilage  by  means  of  a  tough,  fibrous  mem- 
brane. The  Icnver  is  elongated,  and  curved  upon  itself  in  such  a  way  as  to  form 
not  only  half  the  apex,  but  the  outer  and  inner  boundaries  of  the  external  opening 
of  the  nostrils.  Superiorly,  it  is  connected  by  fibrous  membrane  to  the  upper 
cartilage;  internally,  it  is  in  contact  with  its  fellow  of  the  opposite  side,  foiming 
the  upper  part  of  the  columni  nasi ;  posteriorly,  it  is  attached  by  fibrous  tissue  to 
the  maxillary  bone ;  in  this  tissue  are  usually  found  two  or  three  nodules  of  carti- 
lage, called  cartilagiiies  sesamoidcE ;  below,  it  is  firmly  connected  to  dense  connec- 
tive tissue.  By  their  elasticity  these  several  cartilages  keep  the  nostrils  continually 
open,  and  restore  them  to  their  ordinary  size  whenever  they  have  been  expanded 
by  muscular  action. 

The  cartilage  of  the  septum  is  placed  perpendicularly  in  the  middle  hne;  it  may 
lean  a  little,  however,  to  one  side  or  the  other,  and  in  some  instances  it  is  perfo- 
rated, so  that  the  two  nasal  cavities  communicate  with  each  other.  The  cartilage 
is  smooth  and  flat,  and  its  outline  is  nearly  triangular.*  The  posterior  border  is 
received  into  a  groove  in  the  perpendicular  plate  of  the  ethmoid ;  the  anterior  border 
is  much  thicker  than  the  rest  of  the  septum,  and  is  connected,  superiorly,  with  the 
nasal  bones,  and  on  either  side  with  the  lateral  cartilages.  The  inferior  border  is 
attached  to  the  vomer  and  the  median  ridge  at  the  junction  of  the  palatine  pro- 
cesses of  the  maxilla;. 

The  nose  receives  its  blood-supply  from  the  lateralis  nasi,  the  artery  of  the 
septum,  the  facial,  the  nasal  branch  of  the  ophthalmic,  and  the  infra-orbital  arteries. 
The  veins  are  returned  to  the  facial  and  ophthalmic  veins.  The  nerves  are  de- 
rived from  the  nasal  branch  of  the  ophthalmic,  the  infra-orbital,  and infratrochlear 
nerves.     Its  muscles  are  supplied  by  branches  from  the  facial  nerve. 

The  muscles  moving  the  nasal  cartilages  have  been  described  with  the  dissection 
of  the  face  (p.  51). 

Interior  of  the  Nose.  —  A  vertical  section  should  be  made 
throu^di  the  right  nasal  cavity,  a  little  on  the  same  side  of  the 
middle  line,!  to  expose  the  partly  bony  and  partly  catilaginous 
partition  of  the  nasal  cavities  {septum  narium).  Each  nasal 
fossa  is  narrower  above  than  below.     The  greatest  perpendicu- 

»  Cartilage  said  to  be  quadrangular.  Freeman  (Univers.  Med.  Mag.,  vii.,  1895, 
p  332).     A.  H. 

t  This  has  already  been  done  in  order  to  dissect  the  spheno  palatine  ganglion. 


MEATUSES    UF    THE    NOSE, 


79 


lar  depth  of  each  fossa  is  about  the  centre ;  from  this  point  the 
depth  gradually  lessens  towards  the  anterior  and  the  posterior 
openings  of  the  nose.  Laterally,  each  fossa  is  very  narrow,  in 
conseciuence  of  the  projection  of  the  turbinated  bones  towards 
the  septum :  this  narrowness  in  the  transverse  direction  ex- 
plains the  rapidity  with  which  swelling  of  the  lining  membrane 
from  a  simple  cold  obstructs  the  passage  of  air. 

Boundaries  of  Nasal  Fossae.  —  The  nasal  fossae  are 
bounded  by  the  following  bones  :  —  super  iorly,  by  the  nasal, 
the  nasal  spine  of  the  frontal,  the  cribriform  plate  of  the  eth- 
moid, the  body  of  the  sphenoid,  and  the  sphenoidal  turbinated 
bones  :  itifcriorly,  by  the  horizontal  plates  of  the  maxillary  and 
palate  bones  ;  internally,  is  the  smooth  and  flat  septum  formed 
by  the  perpendicular  plate  of  the  ethmoid,  the  ridge  formed  by 


SESAMOID 

CARTILAGES 


CARTILAGE    OF  SEPTUM 
UPPER  LATERAL  CARTILAGE 

LOWER  LATERAL  CARTILAGt 


Fig.  io6.  —  Cartilages  of  the  Nose. 

the  two  nasal  bones,  the  vomer,  the  septal  cartilage,  also  by  the 
nasal  spine  of  the  frontal,  the  rostrum  of  the  sphenoid,  and  the 
crest  of  the  maxillary  and  palate  bones  ;  externally,  by  the  nasal 
process  and  the  inner  surface  of  the  maxillary,  the  lachrymal, 
the  ethmoid,  the  palate,  the  inferior  turbinated  bones,  and  the 
internal  pterygoid  plate  of  the  sphenoid. 

Meatuses  of  the  Nose. — The  outer  wall  of  each  nasal 
cavity  is  divided  by  the  turbinated  bones  into  three  compart- 
ments—  meatuses  —  of  unequal  size;  and  in  these  are  orifices 
leading  to  air-cells  —  sinuses  —  in  the  sphenoid,  ethmoid,  frontal, 
and  maxillary  bones.  Each  of  these  compartments  should  be 
separately  examined. 

a.  The  superior  meatus  is  the  smallest  of  the  three,  and  does 
not  extend  beyond  the  posterior  half  of  the  wall  of  the  nose. 
The  posterior  ethmoidal  and  sphenoidal  cells  open  into  it.     The 


28o  LACHRYMAL    SAC    AND    NASAL    DUCT. 

spheno-palatine  foramen  is  covered  by  the  mucous  membrane, 
and  is  posterior  to  the  meatus. 

b.  The  middle  meatus  is  larger  than  the  superior.  At  its  an- 
terior part  a  long  narrow  passage  (iiifiindibiihmi),  nearly  hidden 
by  a  fold  of  membrane,  leads  upwards  to  the  frontal  and  the 
anterior  ethmoidal  cells.  About  the  middle  a  small  opening 
leads  into  the  antrum  of  the  maxilla :  this  opening  in  the  dry 
bone  is  large  and  irregular,  but  in  the  recent  state  it  is  reduced 
nearly  to  the  size  of  a  crow-quill  by  mucous  membrane,  so  that 
a  very  little  swelling  of  the  membrane  is  sufficient  to  close  the 
orifice  entirely. 

Notice  that  the  orifices  of  the  frontal  and  ethmoid  cells  are  so 
disposed  that  their  secretion  will  pass  easily  into  the  nose.  But 
this  is  not  the  case  with  the  maxillary  cells,  to  empty  which  the 
head  must  be  inclined  on  one  side.  To  see  all  these  openings 
the  respective  turbinated  bones  must  be  raised. 

c.  The  inferior  meatus  extends  nearly  along  the  whole  length 
of  the  outer  wall  of  the  nose.  By  raising  the  lower  turbinated 
bone,  we  observe,  towards  the  front  of  the  meatus,  the  termina- 
tion of  the  nasal  duct,  through  which  the  tears  pass  down  from 
the  lachrymal  sac  into  the  nose.  This  sac  and  duct  can  now 
be  conveniently  examined. 

Lachrymal  Sac  and  Nasal  Duct.  —  The  lachrymal  sac 
and  nasal  duct  constitute  the  passage  through  which  the  tears 
are  conveyed  from  the  canaliculi  into  the  nose  (p.  49).  The 
lachrymal  sae  occn^'xQs  the  groove  formed  by  the  lachrymal  bone 
and  the  nasal  process  of  the  maxilla.  The  upper  end  is  round 
and  closed  ;  the  lower  gradually  contracts  into  the  nasal  duct, 
and  opens  into  the  inferior  meatus.  The  sac  is  composed  of 
a  strong  fibrous  and  elastic  tissue,  which  adheres  very  closely 
to  the  bone,  and  is  lined  by  mucous  membrane,  continuous, 
above,  with  that  lining  the  canalicula,  and  below,  with  that 
of  the  nasal  duct.  Its  front  surface  is  covered  by  the  tendo 
oculli  and  the  fascia  proceeding  from  it,  and  by  the  tensor  tarsi 
muscle. 

The  fiasal  duct  is  from  half  {ij  mm.)  to  three-quarters  {18 
mm.)  of  an  inch  in  length,  and  is  directed  downwards,  back- 
wards, and  a  little  outwards.  Its  termination  is  rather  dilated, 
and  is  guarded  by  a  valvular  fold  of  mucous  membrane —  valve 
of  Hasncr;  consequently,  when  air  is  blown  into  the  nasal  pas 
sages  while  the  nostrils  are  closed,  the  lachrymal  sac  does  not 
become  distended.     The  lachrymal  sac  and  the  nasal  duct  are 


MUCOUS  MEMBRANE  OF  THE  NOSE. 


281 


lined  with  ciliated  epithelium,  and  the  canalicula  with  the 
squamous  variety. 

Behind  the  inferior  turbinated  bone  is  the  opening  of  the 
Eustachian  tube.  Into  this,  as  well  as  into  the  nasal  duct,  we 
ought  to  practise  the  introduction  of  a  probe.  The  chief  diffi- 
culty is  to  prevent  the  probe  from  slipping  into  the  cul-de-sac  be- 
tween the  tube  and  the  back  of  the  pharynx.  (Fig.  107.) 

Mucous  or  Schneiderian  Membrane.  —  This  membrane 
lines  the  cavities  of  the  nose  and  the  air-cells  communicating 


Fig.  107. — Ventrical  Section  of  the  Nasal  Foss.«:  and  Mouth. 

I.  Left  nares.  2.  Labial  cartilage  of  the  nose.  3.  Portion  of  the  internal  alar  cartilage  forming 
the  skeleton  of  the  lower  part.  4.  Superior  meatus.  5.  Middle  meatus.  6.  Inferior  meatus 
7.  Sphenoidal  sinus.  8.  External  boundary  of  the  posterior  nares.  9.  Internal  elliptical 
opening  of  the   Eustachian  tube.     11.    Soft  palate. 

with  it,  and  adheres  very  firmly  to  the  periosteum.  Its  conti- 
nuity may  be  traced  into  the  pharynx,  into  the  orbits  through 
the  nasal  ducts  and  canaliculi,  into  the  various  air  sinuses  — 
viz.,  the  frontal,  ethmoidal,  sphenoidal  sinuses,  and  the  antra  of 
Highmore,  and  into  the  tympana  and  mastoid  cells  through  the 
Eustachian  tubes.  At  the  lower  border  of  the  turbinated  bones 
it  is  disposed  in  thick  and  loose  folds.  The  membrane  varies  in 
thickness  and  vascularity  in  different  parts  of  the  nasal  cavities. 


282 


MUCOUS    MEMBRANE    OF    THE    NOSE. 


Upon  the  lower  half  of  the  septum  and  the  inferior  turbinated 
bones  it  is  much  thicker  than  elsewhere,  owing  to  a  fine  plexus 
of  arteries  and  veins  in  the  submucous  tissue.  In  the  sinuses 
the  mucous  membrane  is  thinner,  less  vascular,  and  closely  ad- 
herent to  the  periosteum. 

The  great  vascularity  of  the  mucous  membrane  raises  the 
temperature  of  the  inspired  air,  and  pours  out  a  copious  secre- 
tion which  prevents  the  membrane  from  becoming  too  dry. 


-/Wh  : 

'">rrtnj;8 

^  ly 

'1 

9 

i 

5 

J — -10 


Fig.  io8.  — Section  (Transverse)  of  the  Nasal  FosS/E. 

I.  Septum  between  t!ie  nasal  fosss.  2.  Anterior  extremity  of  the  middle  turbinated  bone.  i. 
Middle  meatus.  4.  Section  of  the  inferior  turbinated  bone,  made  on  a  level  with  the  opening 
of  the  nasal  canal.  5.  Inferior  meatus.  6.  Lachrymal  sac.  7.  The  two  lachrvmal  canals  uniting 
in  one  to  open  into  the  lachrymal  sac  by  a  common  orifice.  8.  Nasal  canal.  g.  Cut  fold  of 
mucous  membrane  of  this  canal,  showing  its  continuance  with  that  of  the  inferior  meatus  (Valve 
of  Hasner).     10.  Antrum  of  Highmore. 

The  mucous  membrane  of  the  nasal  cavities  is  not  lined  throughout  by  the 
same  kind  of  epithelium.  Near  the  nostrils  the  mucous  membrane  is  furnished 
with  papillae,  with  a  squamous  epithelium  like  the  skin,  and  a  few  small  hairs 
(vibrissa).  In  the  lower  part  of  the  no.'-^e — namely,  alonp;  the  respiratory  tract 
and  in  the  sinuses  —  the  epithelium  is  columnar  and  ciliated ;  but  in  the  true  ol- 
factory ref(ion  —  that  is,  upon  the  superior  and  middle  turbinated  bones  and  the 
upper  half  of  the  septum  — the  epithelium  is  columnar,  but  not  ciliated.  In  this 
region  the  mucous  membrane  is    extremely    vascular,    thick,    and  sinHHed    with 


OLFACTORY    NERVES.  283 

branched  mucous  glands.  The  columnar  epithelial  cells  taper  off  at  their  deep 
ends  into  fine  processes.  Lying  between  these  processes  are  fusiform  cells,  with 
central  well-defined  nuclei,  to  which  the  name  of  olfactory  cells  has  been  given  ; 
and  it  is  probable  that  the  attenuated  processes  which  pass  inwards  from  these 
cells  are  in  direct  connection  with  the  terminal  fibrils  of  the  olfactory  nerves. 

The  arteries  of  the  nasal  cavities  are  derived  from  the  anterior  and  posterior 
ethmoidal  branches  of  the  ophthalmic,  which  supply  the  roof  of  the  nose,  the 
anterior  and  posterior  ethmoidal  cells,  and  the  frontal  sinuses  ;  from  the  nasal 
artery  of  the  internal  maxillary,  which  supplies  the  septum,  the  meatuses  and  the 
turbinated  bones  ;  from  the  posterior  dental  branch  of  the  internal  maxillary,  which 
supplies  the  anti"um.  The  external  nose  is  supplied  by  the  nasal  branch  of  the 
ophthalmic  (p.  73),  the  arteria  lateralis  nasi,  the  angular,  and  the  artery  of  the 
septum. 

The  veins  of  the  nose  correspond  with  the  arteries,  and,  like  them,  form  close 
plexuses  beneath  the  mucous  membrane.  They  communicate  with  the  veins 
within  the  cranium,  through  the  foramina  in  the  cribriform  plate  of  the  ethmoid 
bone;  also  through  the  ophthalmic  vein  and  the  cavernous  sinus.  These  commu- 
nications explain  the  relief  frequently  afforded  by  hemorrhage  from  the  nose  in 
cases  of  cerebral  congestion. 

The  mucous  membrane  of  the  nose  is  supplied  with  sensory  nerves  by  the  fifth 
pair.  Thus,  its  roof  is  supplied  by  filaments  from  the  external  division  of  the 
nasal  branch  of  the  ophthalmic  and  from  the  Vidian;  its  outer  wall,  by  filaments 
from  the  superior  nasal  branches  of  the  spheno-palatine  ganglion,  from  the  nasal, 
from  the  inner  branch  of  the  anterior  dental,  and  from  the  inferior  nasal  branches 
of  the  large  palatine  nerve ;  its  septum,  by  the  septal  branch  of  the  nasal  nerve, 
by  the  nasal  branches  of  the  spheno-palatine  ganglion,  by  the  naso-palatine,  and 
by  the  Vidian ;  its  floor,  by  the  naso-palatine  and  the  inferior  nasal  branches  of 
the  large  palatine  nerve. 

Olfactory  Nerves.  —  The  olfactory  nerves,  proceeding  from 
each  olfactory  bulb,  in  number  about  twenty  on  each  side,  pass 
through  the  foramina  in  the  cribriform  plate  of  the  ethmoid 
bone.  In  its  passage  each  nerve  is  invested  with  a  coat  derived 
from  the  dura.  They  are  arranged  into  an  inner  and  an  outer 
set.  The  septal,  which  are  the  largest,  traverse  the  grooves  in 
the  upper  third  of  the  septum.  The  ^///^r  pass  through  grooves, 
and  are  divided  into  an  anterior  and  a  posterior  group  :  the  an- 
terior being  distributed  over  the  superior  turbinated  bone,  the 
posterior  over  the  os  planum  of  the  ethmoid,  and  the  middle 
turbinated  bone  is  confined  to  the  ethmoid  bone. 

The  nerves  descend  obliquely  between  the  mucous  membrane 
and  the  periosteum,  and  break  up  into  filaments,  which  commu- 
nicate freely  with  one  another,  and  form  minute  plexuses  with 
small  elongated  intervals.  Microscopically,  the  filaments  differ 
from  the  other  cerebral  nerves  in  containing  no  white  substance 
of  Schwann,  and  in  their  axis-cylinders  being  provided  with  a 
very  distinct  nucleated  sheath  with  fewer  nuclei  and  at  longer 
intervals. 


28a  serratus  posticus. 


DISSECTION  OF  THE  MUSCLES  OF  THE.  BACK. 

Dissection  to   Expose   the   Third  Layer  of   Muscles. — 

Those  muscles  of  the  back  —  namely,  the  trapezius,  latissimus 
dorsi,  levator  anguli  scapulae,  and  rhomboidei  —  which  are  con- 
cerned in  the  movements  of  the  upper  extremity  will  be  exam- 
ined in  the  dissection  of  the  arm.  These  must  be  reflected  near 
to  their  insertions,  together  with  the  cutaneous  vessels  and 
nerves.  We  now  proceed  to  examine  the  three  muscles  forming 
the  third  layer  of  muscles,  named,  from  their  appearance,  ser- 
rati postici,  superior,  and  inferior,  and  the  spleniiis.  The  nerves 
and  arteries  will  be  described  after  the  dissection  of  the  sub- 
occipital triangle. 

Serratus  Posticus  Superior.  —  This  muscle  is  situated  be- 
neath the  rhomboidei.  It  is  a  thin  flat  muscle,  and  arises  from 
the  lower  part  of  the  ligamentum  nuchae,*  from  the  spinous 
processes  of  the  last  cervical,  and  two  or  three  upper  thoracic 
vertebrae,  by  a  sheet-like  aponeurosis  which  makes  up  nearly  half 
the  muscle  ;  the  fibres  run  obliquely  downwards  and  outwards, 
and  are  inserted  by  four  fleshy  slips  into  the  second,  third, 
fourth,  and  fifth  ribs  beyond  their  angles.  Its  action  is  to  raise 
these  ribs,  and  therefore  to  assist  in  inspiration.  Is  only 
brought  into  action  in  forced  inspiration. 

Serratus  Posticus  Inferior. — This  muscle  is  situated  in 
the  upper  lumbar  region,  beneath  the  latissimus  dorsi.  It  arises 
by  means  of  the  lumbar  aponeurosis,  from  the  spinous  processes 
of  the  two  last  thoracic  and  two  upper  lumbar  vertebrae  and 
their  supra-spinous  ligament.  It  ascends  obliquely  outwards, 
and  is  inserted  by  four  fleshy  slips  into  the  four  lower  ribs  exter- 
nal to  their  angles.  Its  action  is  to  pull  down  these  ribs,  and 
therefore  to  assist  in  expiration.  Is  only  required  in  forced  ex- 
piration, as  the  ordinary  expiration  is  performed  by  the  elasticity 
of  the  thoracic  and  abdominal  walls  and  their  contents.  The 
posterior  serrati  muscles  are  supplied,  respectively,  by  the  ex- 
ternal branches  of  the  posterior  divisions  of  the  cervical  and 
thoracic  nerves. 

Vertebral  Aponeurosis. — The  thin  aponeurosis  which,  in 

*  The  ligamentum  nuchne  is  a  nidiment  of  the  great  elastic  ligament  of  quad- 
rupeds (termed  the  pack-wax)  which  supports  the  weight  of  the  head.  Tt  pro- 
ceeds from  the  spine  of  the  occiput  to  the  spines  of  all  the  cervical  vertehnu 
except  the  atlas ;  otherwise  it  would  interfere  with  the  free  rotation  of  the  head. 


LUMBAR    FASCIA. 


28s 


the  dorsal  aspect  of  the  thoracic  region,  separates  the  muscles 
of  the  upper  extremity  from  those  of  the  back,  is  called  the 
%'er-tebral  aponeurosis.  Superiorly,  it  is  continued  beneath  the 
splenius,  and  is  continuous  with  the  deep  cervical  fascia  ;  infc- 
riorly,  it  binds  down  the  muscles  contained  in  the  vertebral 
groove,  and  is  attached  to  the  upper  border  of  the  serratus  pos- 
ticus inferior,  and  the  tendon  of  the  latissimus  dorsi ;  internally, 
it  is  attached  to  the  spinous  processes  of  the  thoracic  vertebree, 
and  externally  to  the  angles  of  the  ribs. 

Lumbar  Fascia.  —  This  aponeurosis  consists  of  three  lay- 
ers, of  which  only  the  posterior  layer  can  now  be  seen,  the  other 
two  being;  demonstrated  in  the  dissection  of  the  abdominal  mus- 


ERECTOR     SP 


Fig.  log.  —  Transversb    Section    through    the   Abdomen,   to  show  the   Attachment  op 

THE   Three   Layers  of   the    Lumbar    Fascia    to   the    Transverse   and    Spinous 

Processes  of  the   Lumbar  Vektebr/E. 

cles.  The  dorsal  or  superficial  layer  is  attached  to  the  crest 
of  the  ilium,  to  the  spinous  processes  of  all  the  lower  thoracic, 
lumbar,  and  sacral  vertebrae  ;  it  forms  a  sheath  for  the  erector 
spinae,  and  serves  for  the  attachment  of  the  latissimus  dorsi, 
the  serratus  posticus  inferior,  and  the  internal  oblique. 

The  serratus  posticus  superior  must  now  be  reflected  from 
its  origin,  and  turned  outwards  to  expose  the  following  muscle. 

Splenius.*  —  This  muscle,  so  called  from  its  resemblance  to 
a  strap,  arises  from  the  spinous  processes  of  the  five  or  six 
upper  thoracic  and  the  last  cervical  vertebrae,  from  the  supra- 


*  Sometimes  classified  as  being  the  fourth  layer,  but  in  reality  carries  out  the 
same  function  in  the  cervical  region  as  that  performed  in  the  lumbar  region  by 
the  lumbar  fascia,  and  hence  the  name  applied  to  it,  cTTrX^i'toj'ea,  bandage.  —  A.  H. 


286 


MUSCLES    OF    THE    BACK. 


Fig.  no.  —  The  Superficial   Muscles  of  the  Back. 


SPLENIUS.  287 

spinous  ligament,  and  from  the  lower  half  o.  the  ligamentum 
nuchae.     The  fleshy  fibres  pass  upwards 

and  outwards  and  divide  into  two  por-  g  « 

tions,  named,  according  to  their  respec-  g  ^ 

tive     insertions,    splcnius    capitis    and  g  g 

splenitis  colli.  ^  o 

a.    The  splcnius  capitis,  the  inner  of  w  u 

the   two   portions,  is   inserted  into  the  :^  o 

mastoid  process,  and  into  the  outer  part  ^  os 

of  the  superior  curved  line  of  the  occip-  g 

ital  bone,  beneath  the  sterno-mastoid.  ^ 


H 


•-) 


^^i.    The  splcnius  colli,  the  outer  of  the  •  j 


two   portions,  is   inserted  by  tendinous  2                       u 

slips  into  the  posterior  tubercles  of  the  §                        2 

transverse  processes  of  the  upper  three  '^                       < 

cervical  vertebrae.     The  splenius  is  sup-  ^                        g 

plied  by  the  external   branches  of  the  '^                       « 

posterior  divisions  of  the  cervical  nerves.  p                        < 

The  action  of  the  splenius,  taken  as  a  g                       H 

whole,  is  to  draw  the  head  and  the  upper  g 

cervical  vertebrae  towards  its  own  side;  S                        ^ 

so  far,  it  co-operates  with  the  opposite  . "                         9 

sterno-mastoid     muscle.       When     the  ^                           ^ 

splenii  of  opposite  sides  contract,  they  <                           § 

extend  the  cervical  portion  of  the  spine,  o                           ^ 

and  keep  the  head  erect.     The  perma-  V                           o 

nent  contraction  of  a  single  splenius  may  j                           o 

occasion  wry-neck.     It  is   necessary  to  ^^                       ^    ^ 

be  aware  of  this,  otherwise  one   might  'Ik                  t       [^ 

suppose  the  opposite  sterno-mastoid  to  f^              "^        1^ 

be    affected,    considering   that    the    ap-     .  '^        .^          o 

pearance  of    the   distortion   is   alike   in    ^  ^  -^             "^ 

either  case.                                                       ^  ^^                 S 

ci,  2;  ^ 

Dissection  to  Expose  the  Fourth  Layer.  —     ^  S  tij 

To    lay   bare    the  fourth    layer   of    muscles,    the     '^  ^  ^ 

splenius  and   serratus  posticus    inferior  are   to  be     1^  ai  fe; 

detached  from  their  origins.     After  reflecting  the     ^  ^  '^ 

vertebral   aponeurosis  and  the  lumbar  fascia  from     $  m  s 

its  internal   attachment,  the  erector  spinas  and  its  bj 

prolongations  are  exposed.  W 

Erector  Spinae.*  —  The  mass  of  muscle  which 
occupies  the  vertebral  groove  on  each  side  of  the  ^^s'lt^^f  av^itT  PnofoN^TTioNS 
spine  is,   collectively,   called  erector   spincE,  since  it      into  the   Posterior  Thoracic 
counteracts  the  tendency  of  the  trunk  to  fall  for-     and  Cervical  Regions. 

*  Sometimes  described  as  the  fifth  layer  of  the  muscles  of  the  back. 


288  ERECTOR    SPIN^, 

wards.  It  is  pointed  at  its  lower  tendinous  extremity,  where  it  arises  from  the 
sacral  region  ;  in  the  lumbar  region  it  is  broad,  thick,  and  muscular  ;  in  the  lower 
thoracic  region  it  divides  into  two  portions,  which  are  continued  upwards  with 
additional  muscles  into  the  cervical  vertebras  and  the  head.  Observe  that  it  is 
thickest  and  strongest  at  that  part  of  the  spine  where  it  has  the  greatest  weight 
to  support  —  namely,  in  the  lumbar  region;  and  that  its  thickness  gradually 
decreases  towards  the  top  of  the  spine. 

It  arises  by  thick  tendinous  fibres  from  the  spinous  processes  of  the  two  or  three 
lowest  thoracic  and  of  all  the  lumbar  vert ebrje,  from  the  spines  of  the  sacrum,  from 
the  supraspinous  ligament,  from  the  posterior  fifth  of  the  inner  lip  of  the  crest  of 
the  ilium,  from  the  lower  and  back  part  of  the  sacrum,  and  from  the  posterior 
sacro-iliac  ligament.  From  this  extensive  origin  the  muscular  fibres  ascend,  at 
first  as  a  single  mass.  Near  the  last  rib,  this  mass  divides  into  two :  an  outer, 
called  the  ilio-costalis  or  sacro-lumbalis ;  an  inner,  the  longissii?ins  dorsi.  These 
two  portions  should  be  followed  up  the  back ;  and  there  is  no  difficulty  in  doing 
so,  because  the  division  is  indicated  by  a  longitudinal  groove,  in  which  we  observe 
the  e.xternal  cutaneous  branches  of  the  intercostal  vessels  and  nerves. 

Ilio-costalis  or  Sacro-Lumbalis.  —  Tracing  ihe  ilio-costalis  or  sacro-hcmbalis 
upwards,  we  find  that  it  terminates  in  a  series  of  tendons  which  are  i/iseried  into 
the  angles  of  the  six  lower  ribs. 

Musculus  Accessorius  ad  Ilio-Costalem.  ■ —  By  turning  outwards  the  ilio- 
costalis,  we  observe  that  it  is  continued  upwards  under  the  name  of  muscuhis 
accessorius  ad  ilio-costaletn.  This  arises  by  a  series  of  tendons  from  the  angles 
of  the  si.x  lower  ribs,  internal  to  the  preceding,  and  is  inserted  by  muscular  slip^ 
into  the  angles  of  the  six  upper  ribs. 

Cervicalis  Ascendens.  —  This  is  the  cervical  continuation  of  the  musculus 
accessorius.  It  arises  by  tendinous  slips  from  the  angles  of  the  four  or  five 
upper  ribs,  internal  to  the  musculus  accessorius,  and  is  inserted  into  the  posterior 
tubercles  of  the  transverse  processes  of  the  fourth,  fifth,  and  sixth  cervical 
vertebrae.  • 

Longissimus  Dorsi.*  —  The  longissimus  dorsi  (the  inner  portion  of  the 
erector  spinae)  terminates  in  tendons  which  are  inserted,  internally,  into  the  tuber- 
cles t  at  the  root  of  the  transverse  processes  of  the  lumbar  vertebrse,  into  the 
tubercles  of  the  articular  processes  of  the  same  vertebrae,  of  the  middle  layer  of 
the  fascia  lumborum,  also  into  the  transverse  processes  of  all  the  thoracic  verte- 
brae, and  externally  into  the  greater  number  of  the  ribs  (varying  from  eight  l-o 
eleven)  between  their  tubercles  and  angles. 

Transversalis  Colli.  —  This  is  the  cervical  continuation  of  the  longissimus 
dorsi.  It  arises  by  long  tendinous  slips  from  the  tips  of  the  transverse  processes 
of  the  five  or  six  upper  thoracic  vertebrae,  and  is  inserted  into  the  posterior  tuber- 
cles of  the  transverse  processes  of  the  four  or  five  lower  cervical  vertebrae  except 
the  last. 

Trachelo-mastoid. — This  muscle,  situated  on  the  inner  side  of  the  preceding, 
and  external  to  the  complexus,  is  the  internal  continuation  of  the  longissimus  dorsi 
to  the  cranium.  It  arises  from  the  transverse  processes  of  the  three  or  four 
upper  thoracic  and  the  articular  processes  of  the  three  or  four  lower  cervical  verte- 
brae, and  is  inserted  by  a  flat  tendon  into  the  back  part  of  the  mastoid  process 
beneath  the  splenius.j 

*  Designated  by  Morris  as  the  middle  division  (Loiigissifiius  Dorsi  to  and  in- 
cluding Trachelo-mastoid). 

t    (^alled  anapopliyses  by  I'rofessor  Owen. 

X  Those  who  are  familiar  with  the  transcendental  nomenclature  of  the  verte- 
brate skeleton  will  understand  from  the  following  quotation  the  plan  upon  which 
the  muscles  of  the  back  are  arranged  :  — 

"  The  mu.scles  of  the  back  are  either  longitudinal  or  oblique  ;  that  is,  they  either 
pass  vertically  downwards  from  spinous  process   to  spinous  process,  from  diapo- 


ERECTOR    SPJNyE.  289 

Spinalis  Dorsi.*  —  This  is  a  long  narrow  muscle,  situated  close  to  the  spines 
of  the  thoracic  vertebra,  and  apparently  the  inner  part  of  the  longissimus  dorsi ; 
it  is  bv  some  considered  the  innermost  column  of  the  erector  spina;.  It  arises  by 
tendinous  slips  from  the  spinous  processes  of  the  two  lower  thoracic  and  two  up- 
per lumbar  vertebra;,  and  is  inserted  by  little  tendons  into  the  spinous  processes  of 
the  six  or  eight  upper  thoracic  vertebrae.  Beneath  it  is  the  semispinahs  dorsi, 
which  is  closely  connected  with  the  spinalis  dorsi. 

Spinalis  Colli.  —  This  small,  but  not  constant  muscle  corresponds  in  the  cervi- 
cal region  to  the  spinalis  dorsi  in  the  thoracic  region.  It  arises  by  tendinous  slips 
from  the  spinous  processes  of  the  two  or  three  lower  cervical  vertebra;  (sometimes 
also  from  the  two  upper  thoracic),  and  is  inserted  mto  the  spine  of  the  axis,  and 
occasionally  into  the  spinous  processes  of  the  third  and  fourth  cervical. 

The  muscles  of  the  spine  hitherto  examined  are  all  longitudinal  in  their  direc- 
tion. We  now  come  to  a  series  which  run  obliquely  from  the  transverse  to  the 
spinous  processes  of  the  vertebrc-e.     And  iirst  of  the  complexus. 

Complexus.t  —  This  powerful  muscle  ariseshy  tendinous  sHps  from  the  trans- 
verse processes  of  the  three  or  four  upper  thoracic  and  the  last  cervical  vertebra;, 
also  from  the  articular  processes  of  four  or  live  cervical  vertebra;,  and  their  capsu- 
lar ligaments.  It  is  inserted  between  the  two  curved  lines  of  the  occiput,  near  the 
vertical  crest.  In  the  centre  of  the  muscle  there  is  generally  a  transverse  tendi- 
nous intersection.  The  muscle  is  perforated  by  the  posterior  branches  of  the  second 
(the  great  occipital),  third,  and  fourth  cervical  nerves.  It  is  chiefly  supplied  by 
the  great  occipital  nerve.     Its  action  is  to  maintain  the  head  erect. 

Biventer  Cervicis.  — This  muscle  is  placed  in  the  inner  side  of  the  preceding 
muscle  and  frequently  forms  part  of  it.  It  has  an  intermediate  tendon,  and  arises 
from  the  transverse  processes  of  two  or  three  upper  thoracic  vertebra;,  and  ascends 

pliysis  to  diapop'iysis,  from  rib  to  rib  (pleurapophysis),  etc.,  or  they  extend  obliquely 
from  diapophysis  to  spine,  or  from  diapophysis  to  pleurapophysis,  etc. 

"  The  erector  spinae  is  composed  of  twoplanes  of  longitudinal  fibres  aggregated 
together,  below,  to  form  one  mass  at  their  point  of  origin,  from  the  spines  and 
dorsal  surface  of  the  sacrum,  from  the  sacroiliac  ligament,  and  from  the  dorsal 
third  of  the  iliac  crest.  It  divides  into  two  portions,  the  sacro-lumbalis  and  the 
longissimus  dorsi. 

"  The  foiTTier,  arising  from  the  iliac  crest,  or  from  the  pleurapophysis  (rib)  of 
the  first  sacral  vertebra,  is  inserted  by  short  flat  tendons  into  (i)  the  apices  of  the 
stunted  lumbar  ribs,  close  to  the  tendinous  origins  of  the  transversalis  abdominis; 

(2)  the  angles  of  the  eight  or  nine  infenor  dorsal  ribs  ;  (3)  it  is  inserted,  through 
the  medium  of  the  musculus  accessorius,  into  the  angles  of  the  remaining  superior 
ribs,  and  into  the  long  and  occasionally  distinct  pleurapophysial  element  of  the 
seventh  cervical  vertebra  ;  and  (4)  through  the  medium  of  the  cervicalis  ascendens, 
into  the  pleurapophysial  elements  of  the  third,  fourth,  fifth,  and  sixth  cervical  ver- 
tebra;. In  other  words,  the  muscular  fibres  e.xtend  from  rib  to  rib,  from  the  sacrum 
to  the  third  cervical  vertebra. 

"  The  longissimus  dorsi,  situated  nearer  the  spine  than  the  sacro-lumbalis,  is 
inserted  (I )  into  the  metapophysial  spine  of  the  lumbar  diapophyses;  (2)  into  the 
diapophyses  of  all  the  thoracic  vertebrae,  near  the  origin  of  the  levatorescostarum  ; 

(3)  through  the  medium  of  the  transversalis  colli  into  the  diapophyses  of  the 
second,  third,  fourth,  fifth,  and  sixth  cervical  vertebrae  ;  and  (4)  through  the  me- 
dium of  the  trachelo-mastoid  into  the  mastoid  process,  or  the  only  element  of  a 
transverse  process  possessed  by  the  parietal  vertebra.  In  other  words,  its  fibres 
extend  from  diapophysis  to  diapophysis,  from  the  sacrum,  upwards,  to  the  parietal 
vertebra."  —  Homologies  of  the  Human  Skeleton,  by  H.  Coote,  p.  75. 

*  Designated  by  Morris  as  the  internal  division. 

t  Designated  by  Morris  as  the  sixth  layer.  Complexus,  semispinalis  dorsi, 
semispittalis  colli,  multifidus  spina,  obliquus  capitis  inferior,  obliquus  capitis 
superior,  rectus  capitis  lateralis. 


290 


FIFTH    LAYER, 


between  the  ligamentum  nuchae  and  the  complexus,  to  be  inserted  into  the  inner- 
most depression  between  the  two  curved  lines  of  the  occipital  bone. 

Cut  transversely  through  the  middle  of  the  complexus,  and  reflect  it  to  see  the 

arteria  cervicalis  profunda  (p.  1 36),  and  the  posterior  branches  of  the  cervical  nerves. 

Dissection  to  Expose  the  Fifth   Layer.  —  Remove  the  complexus,  and  then 

turn  aside  the  erector  spince  and  its  prolongations,  when  the  fifth  layer  of  muscles 

wll  be  seen  occuppng  the  interval  between  the  spinous  and  transverse  processes. 

Transverso-spinalis.  —  This  is  the  mass  of  muscle  which  lies  in  the  vertebral 
groove  after  the  reflection  of  the  complexus  and  the  erector  spinse.  It  consists  of 
a  series  of  fibres  which  extend  from  the  transverse  and  articular  processes  to  the 
spinous  processes  of  the  thoracic  and  cervical  vertebras,  and  is  for  convenience 
divided  into  the  semispinalis  dorsi  2l\\A  semispinalis  colli. 

a.  The  semispi  nails  dor  si  arises  by  long  thin  tendinous  slips  from  the  transverse 
processes  of  the  thoracic  vertebrae,  from  the  sixth  to  the  tenth,  and  is  inserted  into 
the  spinous  processes  of  the  four  upper  thoracic  and  the  two  or  three  lower  cervi- 
cal vertebras.  Its  nerves  are  derived  from  the  internal  posterior  branches  of  the 
thoracic  nerves. 

b.  The  semispinalis  colli  lies  beneath  the  complexus,  and  arises  from  the  trans- 
verse processes  of  the  five  or  six  upper  thoracic  vertebrae,  and  the  articular  pro- 
cesses of  the  four  lower  cervical,  and  is  inserted  into  the  spinous  processes  of  the 
axis  and  the  three  or  four  succeeding  vertebras,  that  into  the  axis  being  the  most 
fleshy  fasciculus.  It  is  supplied  by  the  internal  posterior  branches  of  the  cervical 
nerves. 

Now  reflect  part  of  the  semispinalis  dorsi  in  order  to  expose  the  multifidus 
spinas. 

Multifidus  Spinas. —  This  may  be  considered  a  part  of  the  preceding  muscle, 
since  its  fixed  points  and  the  direction  of  its  fibres  are  the  same.  It  consists  of  a 
series  of  little  muscles  which  extend  between  the  spinous  and  transverse  processes 
of  the  vertebrae,  from  the  sacrum  to  the  second  cervical  vertebras.  Those  in  the 
lumbar  region  are  the  largest.  In  the  sacral  region  the  fibres  arise  from  the  dorsum 
of  the  sacrum  as  low  down  as  the  fourth  foramen,  from  the  deep  surface  of  the 
aponeurosis  of  the  erector  spinae,  from  the  inner  part  of  the  posterior  superior 
iliac  spine,  and  from  the  posterior  sacro-iliac  ligament ;  in  the  lumbar  region,  from 
the  mammillary  processes  on  the  superior  articular  processes ;  in  the  thoracic  re- 
gion, from  the  transverse  processes,  and  in  the  cervical  region  from  the  articular 
processes  of  the  four  lower  cervical  vertebras.  They  all  ascend  obliquely,  and 
each  fasciculus  is  inserted  into  the  lamina  and  spinous  process  of  the  vertebra 
above,  except  the  atlas.  It  should  be  observed  that  their  fibres  are  not  of 
uniform  length  ;  some  extend  only  from  vertebra  to  vertebra,  while  others  extend 
between  one,  two,  or  even  three  vertebras.  It  is  supplied  by  the  internal  posterior 
branches  of  the  .sacral,  lumbar,  thoracic,  and  cervical  nerves. 

Rotatores  Spinse.  —  Beneath  the  multifidus  spinae,  in  the  thoracic  region  of 
the  spine  only,  are  eleven  flat  and  somewhat  square  muscles,  called  rotatores  spina:. 
Theyrtrw  from  the  upper  and  back  part  of  the  tran.sverse  processes,  and  are 
inserted  in  to  the  lower  border  of  the  laminas  of  the  vertebra  above.  These  muscles 
form  but  a  part  of  the  multifidus  spinae,  and  are  supplied  by  the  internal  posterior 
branches  of  the  thoracic  nerves. 

The  action  of  the  preceding  muscles  is  not  only  to  assist  in  maintaining  the 
trunk  erect,  but  to  incline  and  rotate  the  spine  to  one  or  the  other  side. 

Levatores  Costarum.  —  These  small  muscles,  twelve  in  number,  on  each  side, 
arise  Ixoxn  the  apices  of  the  transverse  processes  of  the  seventh  cervical  and  the 
eleventh  upper  thoracic  vertebrae,  and  are  inserted  into  the  rib  below.  The  direc- 
tion of  their  fibres  corresponds  with  that  of  the  outer  layer  of  the  intercostal 
muscles,  and  they  are  supplied  by  the  internal  posterior  branches  of  the  thoracic 
nerve.s.     They  are  muscles  of  in.spiration. 

Supraspinales.  — These  are  formed  by  a  series  of  small  mu.scular  slips  l}ing 
over  the  spinous  processes  of  the  cervical  vertebra;.  Their  nerves  are  derived 
from  the  internal  posterior  branches  of  the  cervical  nerves. 


FIFTH    LAYER. 


291 


Inter-spinales.  —  These  muscles  extend  between  the  spinous  processes  of  the 
contiguous  vertebra.  They  are  arranged  in  pairs,  and  only  exist  in  those  parts 
of  the  vertebral  column  which  are  most  movable.  In  the  cervical  region  they 
are  the  most  distinct  and  pass  between  the  spinous  processes  of  the  six  lower 
cervical  vertebra;.  In  the  thoracic  they  are  found  between  the  spinous  processes 
of  the  first  and  second,  and  between  those  of  the  eleventh  and  twelfth  thoracic 
vertebra.  They  are  also  found  more  or  less  distinctly  between  the  spinous  pro- 
cesses of  the  lumbar  vertebra;.  They  are  supplied  by  the  internal  posterior  branches 
of  the  spinal  nerves. 

Inter-transversales.  —  These  muscles  e.xtend  between  the  transverse  processes 
of  the  vertebra;.  In  the  cervical  rci^ion  they  are  seven  in  number,  and  are  most 
marked,  being  arranged  in  pairs,  and  extend  between  the  anterior  and  posterior 
tubercles  of  contiguous  vertebra;.  The  anterior  branch  of  the  corresjjonding  cer- 
vical nerve  separates  the  two  fasciculi.  In  the  thoracic  region  these  muscles  in  the 
upper  part  are  represented  by  small  round  tendons,  but  in  the  three  lower  thoracic 
vertebra;  they  again  become 
muscular  in  stnicture.  In 
the  lumbar  region  the  mus- 
cular fasciculi  are  four  in 
number,  and  are  also  ar- 
ranged in  pairs  between  the 
transverse  processes.  Their 
nerve-supply  is  derived  from 
the  internal  posterior 
branches  of  the  cervical, 
thoracic,  and  lumbar  nerves. 

We  have  next  to  examine 
the  muscles  concemed  in 
the  movement  of  the  head 
upon  the  first  and  second 
cervical  vertebra;  (Fig.  in). 

Rectus  Capitis  Posti- 
cus Major.  —  This  is  a 
largely  developed  inter- 
spinal muscle.  It  ariscshy 
a  small  tendon  from  the 
well-marked  spinous  process 
of  the  second  cervical  verte- 
bra, and,  expanding  con- 
siderably, is  inserted  into 
the  inferior  curved  ridge  of 


Fig.  III.  —  Drawing  from   Nature,  of  the  Si'BOccipital 
Tri.\N(',le. 
the  occipital  bone,  and  into     ■  and  ?•  Complexus.    2.  Rectus  cap.  posticus  minor.    3.  Rectus 


cap.  posticus  major.  4.  Ohliqiius  inferior.  5.  Sterno- 
mastoid.  6.  Semispinalis  colli.  8.  Ohliquus  superior.  10. 
Splenius.  ir.  Trachelo-mastoid.  r2.  Great  occipital  nerve, 
i,^.  Occipital  artery  giving  off  its  descending  branch  —  the 
/iri>ice/>s  cervicis.  14. "Suboccipital  nerve.  15.  Third  cer- 
vical nerve  (posterior  branch). 


the  surface  of  the  bone 
below  it.  These  recti  mus- 
cles, as  they  ascend,  one  on 
each  side,  to  their  inser- 
tions, diverge  and  leave  an 
interval  between  them  in  which  are  found  the  recti  capitis  postici  minores. 

Rectus  Capitis  Posticus  Minor.  — This  is  an  interspinal  muscle,  but  smaller 
than  the  preceding.  Arising  ixova  the  posterior  tubercle  of  the  first  vertebra,  it 
expands  as  it  ascends,  and  is  inserted  into  the  occipital  bone  between  the  inferior 
curved  ridge  and  the  foramen  magnum.  The  action  of  the  two  preceding  muscles 
is  to  raise  the  head.  They  are  supplied  with  nerves  from  the  posterior  branch  of 
the  suboccipital. 

Obliquus  Inferior.  — This^r/j^'j  from  the  spinous  process  of  the  second  cervi- 
cal vertebra,  and  is  inserted  into  the  transverse  process  of  the  first.  Its  action  is 
to  rotate  the  first  upon  the  second  vertebra;  in  other  words,  to  turn  the  head  round 
to  the  same  side.  It  is  supplied  with  a  nerve  by  the  great  occipital  (posterior 
division  of  the  second  cervical),  which  curves  up  under  its  lower  border. 


292  NERVES    OF    THE    BACK. 

Obliquus  Superior.  —  This  muscle  trriscs  from  tlie  transverse  process  of  the 
atlas,  and,  ascending  obliquely  inwards,  is  iiiserkd  in  the  interval  between  the 
curved  ridges  of  the  occipital  bone.  Its  action  is  to  draw  the  occiput  towards  the 
spine. 

Suboccipital  Triangle.  — Observe  that  the  obliqui  (superior  and  inferior)  and 
the  rectus  capitis  posticus  major  form  what  is  called  the  siiboccipitiil  triangle.  The 
outer  side  is  formed  by  the  obliquus  superior;  the  inner,  by  the  rectus  capitis 
posticus  major ;  the  lower,  by  the  obliquus  inferior.  Within  this  triangle  may  be 
seen  the  arch  of  the  atlas,  the  vertebral  artery  lying  in  a  groove  on  its  upper  sur- 
face, and  the  posterior  occipito-atloid  ligament.  Between  the  artery  and  the  bone 
appears  the  posterior  division  of  the  suboccipital  nerve,  which  here  sends  branches 
to  the  recti  postici,  the  obliqui,  and  the  complexus ;  that  is  to  say,  it  supplies  the 
muscles  which  form  the  triangle,  and  the  complexus  that  covers  it. 

Rectus  Capitis  Lateralis.  —  This  small  muscle  extends  between  the  trans 
verse  process  of  the  first  vertebra  and  the  eminentia  jugularis  of  the  occiput ;  but, 
since  this  eminence  is  the  transverse  process  of  the  occipital  vertebra,  the  muscle 
should  be  considered  as  an  intertransverse  one.  Its  nerves  come  from  the  anterior 
division  of  the  suboccipital. 

Nerves  of  the  Back.  —  The  posterior  branches  of  the  spinal  nerves  supply 
the  muscles  and  skin  of  the  back.  They  pass  backwards  between  the  transverse 
processes  of  the  vertebrae,  and  divide  into  external  and  internal  branches.  The 
general  plan  upon  which  these  nerves  are  arranged  is  the  same  throughout  the 
whole  length  of  the  spine ;  but,  since  there  are  certain  peculiarities  deserving  of 
notice  in  particular  situations,  we  must  examine  each  region  separately. 

Cervical  Region.  —  The  posterior  division  of  X^de.  first  cervical  nerve  (the  sub- 
occipital) passes  between  the  arch  of  the  atlas  and  the  vertebral  artery;  it  then 
enters  the  suboccipital  triangle,  and  divides  into  branches  which  supply  the 
muscles ;  one,  which  passes  downwards  to  supply  the  inferior  oblique,  and  also 
sends  downwards  a  branch  to  communicate  with  the  second  cervical  nerve ;  another 
passes  upwards  to  supply  the  recti  capitis  major  and  minor ;  another  supplies  the 
obliquus  superior ;  another  enters  the  complexus ;  and,  lastly,  a  cutaneous  branch 
is  sometimes  given  off  which  accompanies  the  occipital  artery,  and  is  distributed  to 
the  back  of  the  scalp. 

The  posterior  branch  (the  great  occipital)  of  the  second  cervical  nerve  \&  the 
largest  of  the  series,  and  emerges  between  the  arches  of  the  atlas  and  axis.  It 
turns  upwards  beneath  the  inferior  oblique  muscle,  passes  through  the  complexus, 
and  runs  with  the  occipital  artery  to  the  back  of  the  scalp. 

The  posterior  divisions  of  the  six  lower  cervical  nerves  divide  into  cxterttal 
and  internal  branches.  The  external  are  small,  and  terminate  in  the  splenius,  and 
the  continuation  of  the  erector  spina; — viz.,  the  trachelo-mastoid,  the  transver- 
salis  colli,  and  the  cervicalis  ascendens.  The  internal,  by  far  the  larger,  proceed 
towards  the  spinous  processes  of  the  vertebra^ ;  those  of  the  third,  fourth,  and 
fifth  lie  between  the  complexus  and  the  semispinalis,*  and  after  supplying  the 
muscles  terminate  in  the  skin  over  the  trapezius;  those  of  the  sixth,  seventh,  and 
eighth  lie  between  the  semi.spinalis  and  the  multifidus  spinae,  to  which  they  are 
distributed,  and  do  not  as  a  i-ule  give  off  any  cutaneous  branches. 

Thoracic  Region.  —  The  posterior  divisions  of  the  spinal  nerves  in  this  region 
come  out  between  the  transverse  proces.ses  and  the  tendons  attached  to  them.  They 
soon  divide  into  external  and  internal  branches.  The  external  pass  obliquely  over 
the  levatores  costarum,  between  the  ilio-co.stalis  and  the  longi.ssimus  dorsi,  and  suc- 
cessively increase  in  size  from  above  downwards.  The  upper  six  terminate  in  the 
erector  spinne  and  the  levatores  costariim ;  the  lower  six,  after  supplying  these 
muscles,  pass  through  the  lati.ssimus  dorsi,  and  become  the  cutaneous  nerves  of 
the  back.     The  internal  successively  decrease  in  size  from    above    downwards. 

*  The  posterior  branches  of  the  second,  third,  and  fourth  nerves  are  generally 
connected,  beneath  the  complexus,  by  branches  in  the  form  of  loops.  This  con- 
stitutes \he  posterior  cervical  plexus  of  some  other  anatomists. 


NERVES    OK    THE    BACK. 


293 


a,  a,  Small  occipital  nerve 
from  the  cervical  plex- 
us ;   1,  external  muscu- 
lar branches  of  the  first 
cervical  nerve  and  un- 
ion by  a  loop  witli  the 
second  ;    2,  the   rectus 
capitis  posticus  major, 
with  the  great  occipital 
nerve  passing  round  the 
short  muscles  and  pier- 
cing the  complexu.s;  the 
external  branch  is  seen 
to  the  outside  ;    2' ,  the 
great   occipital ;   3,  ex- 
ternal   branch    of    the 
posterior  primary  divi- 
sion of  the  third  nerve; 
3',  its  internal  branch, 
or  third  occipital  nerve: 
4'.  5'.  ^'.  7''  ^' '  '"ternat 
branches  of  the  several 
corresponding     nerves 
on  the  left  side  ;  the  ex- 
ternal branches  of  these 
nerves     proceeding    to 
muscles   are   displayed 
on  the  right  side  :  d  i 
to  ii  b,  and  thence  to  d 
12,   external    muscular 
branches  of  the  poste- 
rior  primary   divisions 
of   the  twelve  thoracic 
nerves  on  the  right  side: 
d  i' ,lodb' ,  the  internal 
cutaneous  branches   of 
the  six  upper   thoracic 
nerves  on  the  left  side  ; 
d  7'  to  d  12',  cutaneous 
branches     of     the     six 
lower    thoracic    nerves 
from    the     external 
branches  ;  /,  /,  external 
branches  of  the  poster- 
ior primary  branches  of 
several   lumbar   nerves 
on  the  right  side  pier- 
cing the  muscles,    the 
lower  descending  over 
the  gluteal  region  ;   /', 
/',  the  same  more  super- 
ficially on  the  left  side  ; 
s,  s,  on  the  right  side, 
the  issue  and  union  by 
loops   of  the  posterior 
primary    divisions     of 

four   sacral  nerves  ,  y, 

s^,  some  of   these  dis- 
tributed to  tlie'skin  on 

the  left  side. 


Fig.  112.— Diagram  of  the  Cutaneous  Nerves  of  the  Back. 


294  ARTERIES    OF    THE    BACK. 

They  run  towards  the  spine  between  the  semispinalis  dorsi  and  the  multifidus 
spina?.  The  upper  si.\,  after  giving  branches  to  the  muscles,  perforate  tlie  trape- 
zius and  become  cutaneous  nerves.  Tire  lower  ones  terminate  in  the  muscles  of 
the  vertebral  groove. 

Lumbar  Region.  —  The  general  arrangement  of  the  nerves  in  this  region 
resembles  that  of  the  thoracic.  Their  external  branches,  after  supplying  the  erector 
spina:,  become  cutaneous,  and  terminate  in  the  skin  over  the  buttock.  The  in- 
ternal branches  supply  the  multifidus  spina;. 

Sacral  Region.  —  The  posterior  divisions  of  the  spinal  nerves  in  this  region 
are  small.  With  the  exception  of  the  last,  they  come  out  of  the  spinal  canal 
through  the  foramina  in  the  back  of  the  sacrum.  The  upper  two  or  three  divide 
into  external  and  internal  branches.  The  internal  terminate  in  the  multifidus 
spince ;  the  exte>-nal  become  cutaneous  and  supply  the  skin  of  the  gluteal  region. 
The  last  two  sacral  nerves  proceed,  without  dividing,  to  the  integument. 

The  Coccygeal  nerve  is  exceedingly  small,  and,  after  joining  a  small  branch 
from  the  last  sacral,  terminates  in  the  skin  over  the  coccyx. 

Arteries  of  the  Back.  —  The  arteries  which  supply  the 
back  are:  i.  Small  branches  from  the  occipital;  2.  Small 
branches  from  the  vertebral ;  3.  The  deep  cervical ;  4.  The 
posterior  branches  of  the  intercostal  and  lumbar  arteries. 

The  occipital  artery  furnishes  several  small  branches  to  the 
muscles  at  the  back  of  the  neck ;  one,  larger  than  the  rest,  the 
arteria  priiiceps  cervicis,  descends  beneath  the  complexus,  and 
generally  inosculates  with  the  deep  cervical  artery,  and  with 
small  branches  from  the  vertebral. 

The  vertebral  artery  runs  along  the  groove  in  the  arch  of  the 
atlas,  and  before  perforating  the  posterior  occipito-atloid  liga- 
ment to  enter  the  skull,  distributes  small  branches  to  the 
adjacent  muscles. 

T\\Q  deep  covical  artery  IS,  the  posterior  branch  of  the  first 
intercostal  artery  (from  the  subclavian).  It  passes  backwards 
between  the  transverse  process  of  the  last  cervical  vertebra  and 
the  first  rib  ;  it  then  ascends  between  the  complexus  and  the 
semispinalis  colli,  and  anastomoses  with  the  princeps  cervicis. 

The  posterior  branches  of  the  intercostal  and  lumbar  arteries 
accompany  the  corresponding  nerves,  and  are  in  all  respects 
similar  to  them  in  distribution.  Each  sends  a  small  branch 
into  the  spinal  canal  (intraspinal),  and  small  branches  to  the 
vertebra. 

The  vei7is  correspond  to  the  arteries. 

Prevertebral  Muscles.  —  We  have,  lastly,  to  examine  three 
muscles,  situated  in  front  of  the  spine :  namely,  the  longus 
colli,  the  rectus  capitis  anticus  major,  and  the  rectus  capitis 
anticus  minor.  In  order  to  have  a  complete  view  of  the  two 
latter,  a  special  di.ssection  should  be  made,  before  the  head  is 
removed  from  the  first  vertebra. 


PREVERTEBRAL    MUSCLES. 


295 


Longus  Colli.  —  This  muscle  is  situated  in  front  of  the  spine, 
and  extends  from  the  third  thoracic  vertebra  to  the  atlas.  For 
convenience  of  description  it  is  divided  into  three  sets  of  fibres, 
of  which  one  extends  longitudinally  from  the  body  of  one  verte- 
bra to  that  of  another ;  the  two  others  extend  obliquely  between 
the  transverse  processes  and  the  bodies  of  the  vertebrae. 

The  longitudinal  portion  of  the  muscle  arises  from  the  bodies 
of  the  three  upper  thoracic  and  the  three  lower  cervical  vertebrae, 
and  is  inseHed  into  the  bodies  of  the  second,  third,  and  fourth 
cervical  vertebrae. 


Fig.  113. — Diagram  of  the  Prevertebral  Muscles. 
1-7.   The  bodies  of  the  cervical  vertehr.-E  :  below  are  the  bodies  of  the  three  upper  thoracic  vertebra. 
a.    Rectus  capitis  lateralis,     b.    Rectus  capitis  anticus   major,     c.    Rectus  capitis  anticus  minor. 
d.    Intertransverse     muscle.      e.     Scalenus   anticus.     f.    Scalenus    medius.    g.    Longus  coin. 
h.   Scalenus  posticus. 

The  superior  oblique  portion,  arising  from  the  anterior  tuber- 
cles of  the  transverse  processes  of  the  third,  fourth,  and  fifth 
cervical  vertebrae,  ascends  inwards,  and  is  inserted  into  the  front 
part  or  body  of  the  atlas.  The  inferior  oblique  portion  proceeds 
from  the  bodies  of  the  three  upper  thoracic  vertebrae,  and  pass- 
ing upwards  and  outwards,  is  inserted  mto  the  transverse  pro- 
cesses of  the  fifth  and  sixth  cervical  vertebrae.     The  action  of 


296  LIGAMENTS    OF    THE    SPINE. 

this  muscle,  taken  as  a  whole,  must  be  to  bend  the  cervical  region 
of  the  spine.      Its  ncivcs  come  from  the  lower  cervical  nerves. 

Rectus  Capitis  Anticus  Major.  —  This  muscle  arises  by- 
tendinous  slips  from  the  anterior  tubercles  of  the  transverse 
processes  of  the  third,  fourth,  fifth,  and  sixth  cervical  vertebrae, 
and,  ascending  obliquely  inwards,  is  inserted  into  the  basilar 
process  of  the  occipital  bone,  in  front  of  the  foramen  magnum. 

Rectus  Capitis  Anticus  Minor.  —  This  muscle  arises  from 
the  front  of  the  root  of  the  transverse  process  of  the  atlas,  and 
is  iiisc7-ted  into  the  basilar  process  of  the  occipital  bone,  nearer 
to  the  foramen  magnum  than  the  preceding  muscle.  The  action 
of  the  recti  muscles  is  to  bend  the  head  forwards.  They  are 
supplied  with  nernes  from  the  anterior  division  of  the  suboc- 
cipital, and  from  the  deep  cervical  plexus, 

LIGAMENTS    OF   THE    SPINE. 

The  vertebrae  are  connected  by  their  intervertebral  fibro-car- 
tilages,  by  ligaments  in  front  of  and  behind  their  bodies,  and  by 
ligaments  which  extend  between  their  arches  and  their  spines. 
Their  articular  processes  have  capsular  ligaments  and  synovial 
membranes. 

Anterior  Common  Ligament.  —  This  is  a  strong,  broad 
band  of  longitudinal  fibres  which  extends  along  the  front  of  the 
bodies  of  the  vertebrae  from  the  occipital  bone  to  the  sacrum. 
The  ligament  is  broader  below  than  above,  thickest  in  the  tho- 
racic region,  and  its  fibres  are  more  firmly  adherent  to  the  inter- 
vertebral cartilages  and  to  the  borders  of  the  vertebrae  than  to 
the  middle  of  the  bones.  The  fibres  are  not  all  of  equal  length  ; 
the  more  superficial  extend  from  one  vertebra  to  the  fourth  or 
fifth  below  it ;  those  a  little  deeper  pass  from  one  vertebra  to 
the  second  or  third  below  it,  while  the  deepest  of  all  proceed 
from  vertebra  to  vertebra.  Above,  it  is  attached  to  the  axis  by 
a  pointed  process,  where  it  is  connected  with  the  longus  colli, 
and  it  is  thicker  over  the  bodies  of  the  vertebra  than  over  the 
intervertebral  cartilages,  thus  filling  up  the  concavities  of  the 
bodies  and  rendering  the  surface  more  smooth  and  even.* 

Posterior  Common  Ligament. — This  extends  longitudi- 
nally, in    a  similar  manner  to  the  anterior  common  ligament, 

*  The  student  should  remember  that  the  anterior  and  posterior  common  liga- 
ments are  in  reality  continuous,  and  also  that  the  deeper  portions  of  these  ligaments 
form  firm  attachments  for  the  disks  of  cartilage.  —  A.  H. 


INTERVERTEBRAL    FIBRO-CARTILAGE.  297 

within  the  spinal  canal,  along  the  posterior  surface  of  the  bodies 
of  the  vertebras,  from  the  occii)ital  bone  to  the  sacrum.  It  is 
broader  above  than  below,  and,  like  the  anterior  ligament,  is 
thickest  in  the  thoracic  region,  and  is  more  intimately  connected 
with  the  intervertebral  fibro-cartilages  than  with  the  bodies  of 
the  vertebrae.  It  sends  up  a  prolongation  to  the  anterior  border 
of  the  foramen  magnum  continuous  with  the  apparatus  liga- 
mentosus. 

Interspinous  Ligaments. — These  bands  of  ligamentous 
fibres  fill  up  the  intervals  between  the  spines  of  the  thoracic  and 
lumbar  vertebme.     They  are  most  marked  in  the  lumbar  region.* 

Supraspinous  Ligament.  — Those  fibres  which  connect  the 
apices  of  the  spines,  being  stronger  than  the  rest,  are  described 
as  a  separate  ligament  under  the  name  of  supraspinous.  It  ex- 
tends from  the  spinous  process  of  the  seventh  cervical  to  the 
spine  of  the  sacrum,  and  is  strongest  in  the  lumbar  region. 
Their  use  is  to  limit  the  flexion  of  the  spine. 

Ligaments  between  the  Arches  of  the  Vertebrae.  —  These 
are  called,  on  account  of  their  color,  liganicnta  subjlava.  To 
obtain  a  good  view  of  them  the  arches  of  the  vertebrae  should 
be  removed  with  a  saw,  and  the  ligaments  should  be  seen  from 
within,  since  viewed  from  without  they  are  to  a  large  extent 
hidden  by  the  overlapping  laminae.  They  pass  between  the 
laminae  of  the  contiguous  vertebrae  from  the  axis  to  the  sacrum  ; 
none  existing  between  the  occiput  and  the  atlas,  or  between  the 
atlas  and  the  axis.  Each  ligament  consists  of  two  halves  which 
are  attached  to  the  corresponding  half  laminae  above  and  below 
on  each  side.  They  are  composed  of  yellow  elastic  tissue,  the 
fibres  being  arranged  vertically,  and  their  strength  increases 
with  the  size  of  the  vertebrae.  This  elasticity  answers  a  double 
purpose ;  it  not  only  permits  the  spine  to  bend  forwards,  but 
materially  assists  in  restoring  it  to  its  curve  of  rest.  They  econ- 
omize muscular  force,  like  the  ligamentum  nuchae  in  animals. 

Intervertebral  Fibro-cartilage. — ^This  substance,  placed 
between  the  bodies  of  the  vertebrae,  is  by  far  the  strongest  bond 
of  connection  between  them,  and  fulfils  most  important  pur- 
poses in  the  mechanism  of  the  spine.  Its  peculiar  structure  is 
adapted  to  break  shocks  and  to  render  the  spine  flexible  and 
resilient.  To  see  the  structure  of  an  intervertebral  fibro-carti- 
lage, a  horizontal  section  must  be  made  through  it.     It  is  firm 

*  The  interspinous  ligaments  are  replaced  in  the  cervical  region  by  the  inter- 
spinals muscles.  —  A.  H. 


298  INTERVERTEBRAL    FIBRO-CARTILAGE. 

and  resisting  near  the  circumference,  but  soft  and  pulpy  towards 
the  centre.  The  circumferential  portion  is  composed  of  concen- 
tric layers  of  fibro-cartilage,  placed  vertically.  These  layers  are 
attached  by  their  edges  to  the  vertebras ;  they  gradually  de- 
crease in  number  from  the  circumference  towards  the  centre  ; 
and  the  interstices  between  them  are  filled  by  soft  pulpy  tissue. 
The  central  portion  is  composed  almost  entirely  of  this  pulpy 
tissue,  and  it  bulges  when  no  longer  under  pressure.  Thus  the 
bodies  of  the  vertebras,  in  their  motions  upon  each  other,  revolve 
upon  an  elastic  cushion  tightly  girt  all  round  by  bands  of  fibrous 
tissue.     These  motions  are  regulated  by  the  articular  processes. 

Dissect  an  intervertebral  substance  layer  after  layer  in  front, 
and  you  wil^  find  that  the  circumferential  fibres  extend  obliquely 
between  the  vertebrae,  crossing  each  other  like  the  branches  of 
the  letter  X  (Fig.  116,  p.  303). 

The  thickness  of  the  intervertebral  cartilages  is  not  the  same 
in  front  and  behind.  It  is  this  difference  in  their  thickness, 
more  than  that  in  the  bodies  of  the  vertebrae,  which  produces 
the  several  curves  of  the  spine.  In  the  lumbar  and  cervical 
regions  they  are  thicker  in  front ;  in  the  thoracic  region,  behind. 

The  structure  of  the  intervertebral  cartilages  explains  the  well- 
known  fact  that  a  man  becomes  shorter  after  standing  for  some 
hours,  and  that  he  regains  his  usual  height  after  rest.  The  dif- 
ference between  the  morning  and  evening  stature  amounts  to 
more  than  half  an  inch  (/j>  vwi.). 

It  also  explains  the  fact  that  a  permanent  lateral  curvature  of 
the  spine  may  be  produced  (especially  in  the  young)  by  the 
habitual  practice  of  leaning  to  this  or  that  side.  Experience 
proves  that  the  cause  of  lateral  curvature  depends  more  fre- 
quently upon  some  alteration  in  the  structure  of  the  fibro-carti- 
lages  than  upon  the  bones.  From  an  examination  of  the  bodies 
of  one  hundred  and  thirty-four  individuals  with  crooked  spines, 
it  was  concluded  that,  in  two-thirds,  the  bones  were  perfectly 
healthy  ;  that  the  most  frequent  cause  of  curvature  resided  in 
the  intervertebral  substances,  these  being,  on  the  concave  side 
of  the  curve,  almost  absorbed,  and,  on  the  convex  side,  preter- 
naturally  developed.  As  might  be  expected  in  these  cases,  the 
muscles  on  the  convex  side  become  lengthened,  and  degenerate 
in  structure.* 

*  On  this  subject  see  Hildebrandt's  Anaiotnie,  B.  ii,  s.  155.  The  aggregation 
of  the  vertebral  disks  is  one-fourth  the  total  length  of  the  column,  and  changes 
the  direction  of  its  curves.     This  is  most  marked  in  the  aged,  when  a  concavity 


MOVEMENTS    OF    THE    SPINE.  299 

Ligamentum  Nuchae.  —  This  ligament  is  a  thin,  triangular, 
fibrous  septum,  intermingled  with  clastic  tissue,  situated  in  the 
middle  line,  and  extends  from  the  spinous  processes  of  the 
seventh  cervical  vertebrae  to  the  chest  and  external  occipital  pro- 
tuberance. It  forms  an  intermuscular  septum  down  the  back  of 
the  neck,  and  may  be  regarded  as  the  continuation  upwards  of 
the  supraspinous  ligament. 

Capsular  Ligaments. — Each  joint  between  the  articular 
processes  has  a  synovial  membrane  surrounded  by  loose  liga- 
mentous fibres,  forming  a  capsular  ligament  which  is  longest  in 
the  cervical  vertebrae,  thus  allowing  free  movement  in  this  re- 
gion.    The  surfaces  of  the  bones  are  crusted  with  cartilage. 

Intertransverse  Ligaments. — These  are  thin  ^ands  of 
fibres  which  pass  between  the  transverse  processes  of  the  ver- 
tebrae. They  are  rudimentary  in  the  cervical  region,  and  are 
sometimes  absent.* 

Movements  of  the  Spine.  — Though  but  little  movement  is 
permitted  between  any  two  vertebrae  (the  atlas  and  axis  ex- 
cepted), yet  the  collective  motion  between  them  all  is  consider- 
able. The  spine  can  be  bent  forwards,  backwards,  or  on  either 
side ;  it  also  admits  of  slight  rotation.  In  consequence  of  the 
elasticity  of  the  intervertebral  cartilages  and  the  ligamenta  sub- 
flava,  it  returns  spontaneously  to  its  natural  curve  of  rest  like 
an  elastic  bow.  Its  mobility  is  greatest  in  the  cervical  region, 
on  account  of  the  thickness  of  the  fibro-cartilages,  the  small  size 
of  the  vertebrae,  the  oblique  direction  of  their  articulations,  and, 
above  all,  the  horizontal  position  and  the  shortness  of  their 
spines.  In  the  thoracic  region  there  is  very  little  mobility,  on 
account  of  the  vertical  direction  of  the  articular  processes,  and 
the  manner  in  which  the  arches  and  the  spines  overlap  each 
other.  In  the  lumbar  region,  the  spine  again  becomes  more 
movable,  on  account  of  the  thickness  of  the  intervertebral  car- 
tilages, and  the  horizontal  direction  of  the  spinous  processes. 

Ligaments  bet^A/■een  the  Occipital  Bone  and  the  Atlas. 
—  The  occiput  is  connected  to  the  atlas  by  the  following  liga- 
ments :  viz.,  two  anterior  occipito-atloid,  or  occipito-atlantal,  a 
posterior  occipito-atloid,  or  occipito-atlantal,  two  lateral  occipito- 
atloid,  or  occipito-atlantaly  and  two  capsular  ligaments. 

may  exist  below  the  centre  of  the  thoracic  region,  due  to  the  absorption  of  the 
anterior  or  ventral  portion  of  the  disk  from  pressure,  according  to  the  occupation 
or  habit  of  the  individual.  —  A.  H. 

*  In  the  cervical  region  these  ligaments  are  replaced  by  intertransversales  mus- 
cles, and  can  only  be  well  demonstrated  in  the  lumbar  region.  —  A.  II. 


300  LIGAMENTS    BETWEEN    OCCIPITAL    BONE    AND    AXIS. 

The  tzuo  anterior  or  occipito-atlantal  ligaments  *  are  composed 
of  a  superficial  and  a  deep  portion;  the  superficial  part  is  a 
strong  rounded  cord  which  passes  from  the  basilar  process 
above,  to  the  tubercle  on  the  anterior  arch  of  the  atlas  below ; 
the  deep  portion  is  membranous,  and  passes  from  the  anterior 
margin  of  the  foramen  magnum  to  the  front  arch  of  the  atlas. 

The  posterior  occipito-atlantal  ligament  extends  in  a  similar 
manner  from  the  posterior  border  of  the  foramen  magnum  to 
the  posterior  arch  of  the  atlas.  It  is  thin,  and  superiorly  be- 
comes blended  with  the  dura,  and  is  pierced  by  the  vertebral 
artery  and  the  suboccipital  nerve. 

The  tzvo  lateral  occipito-atlantal  ligaments  pass  from  the 
jugular  eminences  of  the  occiput  downwards  and  outwards  to 
the  transverse  processes  of  the  atlas. 

The  capsular  occipito-atlantal  ligaments  extend  from  the  mar- 
gin of  the  condyles  of  the  occipital  bone  to  the  upper  articular 
borders  of  the  atlas. 

The  movements  which  take  place  between  the  occipital  bone 
and  the  atlas  are  flexion  and  extension,  as  in  nodding  forwards 
and  backwards ;  and  lateral  movement,  as  in  inclining  the  head 
sideways. 

Ligaments  between  the  Occipital  Bone  and  the  Axis. — 
These  are  the  most  important ;  and  to  see  them,  make  a  vertical 
transverse  section  through  the  occipital  bone  in  the  posterior 
third  of  the  foramen  ^magnum,  dividing  the  pedicles  near  the 
bodies  of  the  cervical  vertebrae.  The  superficial  portion  of  the 
posterior  common  vertebral  ligament  must  then  be  removed, 
exhibiting  the  occipito-cervical  ligament,  i.  e.,  the  deeper  portion 
of  the  posterior  common  vertebral  ligament  which  extends  from 
the  dorsal  or  posterior  surface  of  the  third  vertebra  to  the 
basilar  groove  of  the  occipital  bone  ;  the  crucial,  the  vertical 
portion  of  the  tra^isverse  ligament  holding  the  odontoid  process 
in  contact  with  the  atlas,  passing  from  the  base  of  the  odontoid 
process  to  the  basilar  surface  of  the  foramen  magnum.  It  is 
difficult  often  to  make  this  dissection  because  of  the  intimate 
relation  of  the  occipito-cervical  ligament.  (A.  H.)  It  is  called 
the  occipito-axial  ligament,  or  the  apparatus  ligamejitosus  colli. 

Odontoid  or  Check  Ligaments.  —  The  odontoid  or  cJieck 
ligaments  (Fig.  i  14)  are  two  very  strong  ligaments,  which  pro- 
ceed from  the  sides  of  the  odontoid  process  to  the  tubercles  on 
the  inner  sides  of  the  condyles  of  the  occiput.     Their  use  is  to 

*  These  ligaments  are  by  some  authors  described  as  one. — A.  H. 


ARTICULATION    BETWEEN    THE    ATLAS    AND    THE    AXIS.     3OI 

limit  the  rotation  of  the  head.  A  tJiird  or  middle  odontoid  lig- 
ament passes  from  the  apex  of  the  odontoid  process  to  the  mar- 
gin of  the  foramen  magnum.  It  is  sometimes  called  the  liga- 
mentitin  siipoisorium. 

Articulation  Between  the  Atlas  and  the  Axis.  —  This 
joint  forms  a  lateral  ginglymus  or  diarthrosis  rotatoria,  and  is 
maintained  by  the  following  ligaments :  two  anterior  atlo-axial, 
a  posterior  atlo-axial,  two  capsular,  and  a  transverse. 


Occipito-cervical 
"igament,  i.  e., 
the  deep  stratum 
of  the  posterior 
common  verte- 
bral ligament. 


Transverse  process  of  atlas. 


Atlanto-axoidean  capsular 
ligament. 


Fig.  114. — The  Superficial  Layer  of  the    Posterior  Common  Vertebral  Ligament 

HAS  BEEN    REMOVED  TO   SHOW    ITS    DeEP    OR   ShORT  FiBRES.      ThESE    DeeP    FiBRBS    FORM 

THE  Occipito-Cekvical   Ligament.     (Morris.) 

The  tivo  anterior  atlanto-axoideaii  ligaments  *  consist  of  a 
superficial  and  a  deep  portion  :  the  superficial  is  a  rounded  liga- 
ment passing  from  the  tubercle  of  the  atlas  to  the  base  of  the 
odontoid  process  ;  the  deep  passes  as  a  membranous  layer  from 
the  anterior  arch  of  the  atlas  to  the  body  of  the  axis. 


*  These  ligaments  are  often  described  as  one. —  A.  H. 


302        ARTICULATION    BETWEEN    THE    ATLAS    AND    THE    AXIS. 

^\\Q  posterior  atlanto-axoidcan  ligamenl  QxtQwds  from  the  pos- 
terior arch  of  the  atlas  to  the  upper  border  of  the  lamina  of  the 
axis. 

The  tzvo  lateral  eapsiilar  ligaments  are  thin,  loose,  ligamen- 
tous sacs  connecting  the  borders  of  the  articular  surfaces. 

The  trajisverse  ligament  (Fig.  1 15)  passes  transversely  behind 
the  odontoid  process  and  is  attached  to  the  tubercles  on  the 


Vertical   portion 
crucial  ligament. 
Central  odontoid 

ligament. 
Lateral   odontoid 
ligament. 
Transverse   portion 
of  crucial  ligament 

Accessory  band  of  atlanto- 
axoidean  capsules. 
Atlanto-axoidean  joint. 


Ocoipito-cervical    or  cervico 
basilar  ligament. 

Posterior  common  ligament, 


Fig.  113.  —  Vertical  Transverse   Section   of    the    Spinal  Column   and  the  Occipital 
Bone  to  show  Ligaments.     (Morris.) 

inner  sides  of  the  articular  processes  of  the  atlas.  From  the 
centre  of  this  ligament  a  few  fibres  pass  upwards,  to  be  attached 
to  the  basilar  process,  and  some  downwards  to  the  body  of  the 
axis,  giving  it  a  cruciform  appearance.  Thus  it  forms  with  the 
atlas  a  ring,  into  which  the  odontoid  process  is  received.  If 
this  transverse  ligament  be  divided,  we  observe  that  the  odon- 
toid process  is  covered  with  cartilage  in  front  and  behind,  and 
is  provided  with  two  (atlanto-odoiitoid  capsular  ligaments)  syno- 
vial membranes. 


ARTICULATIONS    OF    THE    HEADS    OF    THE    RIBS.  3O3 

The  ribs  articulate  by  their  heads  with  the  bodies  of  the  tho- 
racic vertebrae;  by  their  necks  and  tubercles  with  the  trans- 
verse processes  of  the  vertebrae,  and  by  their  cartilages  with  the 
sternum  in  front. 

Articulations  of  the  Heads  of  the  Ribs  with  the  Bodies 
of  the  Vertebrae.  —  The  head  of  each  rib  presents  two  articu- 
lar surfaces,  corresponding  to  the  bodies  of  two  vertebrae. 
There  are  two  distinct  articulations,  each  provided  with  a  sepa- 
rate synovial  membrane.     The  ligaments  are  — 

I.  An  anterior  costo-ccntral  or  stellate,  which  connects  the 
front  of  the  head  of  the  rib  with  the  sides  of  the  bodies  of  two 
vertebrae  and  the  intervening  fibro-cartilage  (Fig.  1 16).  It  is 
composed  of  three  fasciculi  of  fibres  which  radiate  from  the  rib, 
one  of  which  passes  upwards  to  be  attached  to  the  body  of  the 


[.Superior  costo-trans- ^^=**^  Vflfc^^^ifei    l*     //    it  2,  2i  z-  Anterior  costo-central 

verse  ligaments.  ^]0>^^|Bmljb.     ..MimL         or  stellate  ligaments. 


Fig,  h6. —  Costo-vertebral  Ligaments. 

vertebra  above  ;  the  lower  one  passes  to  the  body  of  the  verte- 
bra below;  while  the  intermediate  one  passes  horizontally  for- 
ward to  the  intervertebral  disk. 

In  the  three  lower  ribs  the  fasciculi  are  not  separately  dis- 
tinguishable, although  the  fibres  pass  upwards  to  the  vertebrae 
and  downwards  to  the  vertebra  with  which  the  rib  articulates. 

Some  anatomists  describe  a  capsular  ligament  surrounding 
the  articulation  ;  the  fibres  are  very  thin,  and  form  part  of  the 
costo-central  ligament. 

2.  An  i)itei'aj'ticular  ligament  which  passes  across  the  joint 
from  the  ridge  on  the  head  of  the  rib  to  the  intervertebral  car- 
tilage. It  divides  the  articulation  into  two  joints  which  do  not 
communicate  with  each  other.  It  is  absent  in  the  three  lower 
articulations. 

Articulations  of  the  Neck  and  Tubercle  of  the  Ribs  with 
the  Transverse  Processes.  —  The  lig^aments  connecting  these 


304  THE    CARTILAGES    OF    THE    RIBS. 

bones  are  the  capsular,  the  anterior,  middle,  and  posterior  costo- 
transverse. 

The  capsular  ligament  surrounds  the  articular  surfaces  of  the 
tubercle  of  the  rib  and  the  transverse  process  of  its  correspond- 
ing vertebra,  and  has  a  synovial  membrane.  It  is  absent  in  the 
eleventh  and  twelfth  ribs. 

The.  ventral  or  superior  costo-transverse  ligament  ascends 
from  the  upper  border  of  the  neck  of  the  rib  to  the  lower  bor- 
der of  the  transverse  process  above  it.  It  is  continuous  exter- 
nally with  the  aponeurosis  covering  the  external  intercostal 
muscle.  The  first  and  twelfth  ribs  have  no  anterior  costo- 
transverse ligament  (Fig.  116). 


Fig.  117.  —  Diagram  showing  the  Ligaments  connecting  the    Rib  with  the  Vertebra. 

I.  The  anterior  costo-central  ligament.  2.  The  interosseous,  or  middle  costo-transverse  liga- 
ment. 3.  The  posterior  costo-transverse  ligament.  4.  The  sjmovial  membrane  between  the 
rib  and  the  body  of  the  vertebra. 

The  middle  costo-transverse  ligament  is  an  interosseous  one, 
and  connects  the  adjacent  surfaces  of  the  neck  of  the  rib,  and 
the  transverse  process.  It  is  badly  developed  in  the  eleventh 
and  twelfth  ribs  (Fig.  117). 

The  dorsal  costo-transverse  ligament  passes  from  the  apex  of 
the  transverse  process  to  the  summit  of  the  tubercle  of  the  rib. 
It  is  wanting  in  the  eleventh  and  twelfth  ribs  (Fig.  117). 

Connection  Between  the  Cartilages  of  the  Ribs  and 
Sternum. — The  ventral  extremities  of  the  ribs  are  concave, 
and  receive  the  cartilages  of  the  ribs  ;  this  junction  is  main- 
tained by  the  periosteum.  The  cartilages  of  all  the  true  ribs 
arc  received  into  slight  concavities  on  the  side  of  the  sternum, 
and  are  secured  by  anterior,  posterior,  upper,  and  lower  ligaments. 
There  is  a  synovial  membrane  between  the  cartilage  of  each 
rib  and  the  sternum,  except  that  of  the  first,  and  usually  at  each 


ARTICULATION    OF    THE    MANDIBLE. 


305 


articulation  the  synovial  membrane  is  separated  into  two  by  an 
interarticular  ligament. 

The  costal  cartilages  from  the  sixtJi  to  the  tenth  are  connected 
by  ligamentous  fibres.  There  are  intercostal  synovial  mem- 
branes in  front  between  the  adjacent  borders  of  the  sixth,  sev- 
enth, eighth,  and  ninth  costal  cartilages. 

Movements  of  the  Ribs.  —  The  movements  permitted  be- 
tween the  heads  of  the  ribs  and  the  bodies  of  the  vertebrae  are 
those  of  elevation  and  depression,  and  those  of  rotation  forwards 
and  backwards  ;  the  centre  of  these  movements  being  at  the 
interarticular  ligament.     Between  the  tubercles  and  the  trans- 


Section  through  the  glenoid 
cavity. 


Interarticular  fibro-cartilage.  ;^^^>f 


Internal  lateral  or  spheno- 
maniiibular  ligament. 


Fig.  118.  —  Transverse  Section  to  show  the  Ligaments  and  the  Fibro-Cartilage  of 
THE  Tempero-Mandibular  Joint.  The  Dotted  Lines  represent  the  two  Synovial 
Membranes. 

verse  processes  there  is  the  movement  of  an  arthroidal  nature, 
and  between  the  costal  cartilages  and  the  sternum  that  of  ele- 
vation and  depression. 

The  movement  of  the  first  rib  is  very  slight ;  that  of  the 
second  is  freer  ;  and  mobility  of  the  ribs  gradually  increases 
from  above  downwards. 

Articulation  of  the  Mandible.  —  The  condyle  of  the  man- 
dible articulates  with  the  glenoid  cavity  of  the  temporal  bone, 
and  forms  an  arthroidal  joint.  The  joint  is  provided  with  an 
interarticular  fibro-cartilage,  with  external  and  internal  lateral 
and  capsular  ligaments,  and  two  synovial  membranes  (Fig.  118). 


306  ARTICULATION    OF    THE    MANDIBLE. 

The  extcvjial  lateral  tcmpero-mandibiilar  ligament  is  the  thick- 
est portion  of  the  capsule,  extending  from  the  zygoma  and  its 
tubercle  ;  its  fibres  pass  downwards  and  backwards  to  the  outer 
surface  and  posterior  border  of  the  neck  of  the  mandible. 

The  internal  lateral  or  spJieno-^nandibular  ligament —  a  long, 
thin,  flat  band — extends  from  the  spinous  process  of  the  sphe- 
noid bone  to  the  inner  border  of  the  dental  foramen.  This  lig- 
ament therefore  differs  from  the  external  ligament  in  that  it 
has  no  connection  with  the  capsule.  It  should  always  be  re- 
membered that  the  mandibular  artery  is  between  the  internal 
lateral  or  spheno-mandibular  and  the  mesial  portion  of  the  cap- 
sule. —  A.  H. 

The  capsular  ligament  consists  of  a  few  scattered  fibres  at- 
tached above  to  the  margin  of  the  glenoid  cavity,  below  to  the 
neck  of  the  mandible. 

The  interartic2ilar  fibro-ca7'tilage  is  a  thin  plate  of  an  oval 
form,  and  thicker  at  the  margin  than  at  the  centre.  It  is  placed 
horizontally,  and  its  upper  surface  is  concavo-convex  from  before 
backwards  ;  its  lower  surface  is  concave.  It  is  connected  on 
the  outer  side  to  the  external  lateral  ligament,  and  on  the  inner 
side  some  of  the  fibres  of  the  external  pterygoid  muscle  are 
inserted  into  it. 

There  are  two  synovial  mem,branes  —  an  upper  and  a  lower  — 
for  the  joint.  The  larger  and  looser  of  the  two  is  situated  be- 
tween the  glenoid  cavity  and  the  fibro-cartilage.  The  lower  is 
interposed  between  the  fibro-cartilage  and  the  condyle  of  the 
mandible.  They  sometimes  communicate  through  a  small  aper- 
ture in  the  centre  of  the  fibro-cartilage. 

The  form  of  the  articulation  of  the  mandible  admits  of  move- 
ment upwards  and  downwards,  forwards,  backwards,  and  from 
side  to  side,  A  combination  of  these  movements  takes  place  in 
mastication  ;  during  this  act  the  condyles  of  the  mandible  de- 
scribe an  oblique  rotary  movement  in  the  glenoid  cavity.  The 
purposes  served  by  the  fibro-cartilage  in  this  joint  are  :  first,  it 
follows  the  condyle,  and  interposes  a  convenient  socket  for  all 
its  movements ;  second,  being  elastic,  it  breaks  shocks ;  for 
shocks  here  would  be  almost  fatal,  considering  what  a  thin  plate 
of  b9ne  the  glenoid  cavity  is,  and  that  jnst  above  it  is  the  brain. 
Its  nerves  are  derived  from  the  auriculo-temporal  and  the  mas- 
seteric branches  of  the  mandibular. 

The  stylo-hyoid  and  stylo-mandibular  ligaments  have  been 
previously  described. 


SURFACE    MARKING  307 


DISSECTION    OF    THE    UPPER    EXTREMITY. 

The  subject  should  be  placed  on  its  back,  and,  the  thorax 
being  raised  by  a  block  placed  under  the  shoulders,  the  arm  is 
to  be  extended  to  a  right  angle  with  the  trunk  and  slightly  ro- 
tated outwards.  A  narrow  board  must  be  placed  under  the 
arm  to  keep  it  in  position,  and  the  hand,  with  the  palm  upwards, 
is  to  be  firmly  encircled  by  bandage  to  the  board. 

Surface  Marking. — Before  commencing  the  dissection  of 
the  arm,  the  student  should  carefully  examine  with  the  eye  and 
the  finger  the  various  inequalities  of  the  surface  of  the  skin, 
which  are  caused  by,  or  are  landmarks  of,  important  subjacent 
structures. 

Beginning  in  the  middle  line,  we  notice  a  broad,  shallow 
groove  in  front  of  the  sternum  between  the  sternal  origins  of 
the  pectoralis  major;  about  two  inches  (5  cm.)  below  the  upper 
border  of  the  sternum  is  a  prominent  transverse  bony  ridge 
(angulus  sterni),  which  corresponds  to  the  junction  of  the  first 
and  second  portions  of  the  sternum. 

The  clavicle  may  be  easily  traced,  convex  as  to  its  sternal 
half,  and  concave  in  its  outer  half  ;  not  placed  quite  horizontally, 
but  inclined  upwards  in  the  present  position  of  the  limb,  and 
articulating  externally  with  the  prominent  acromion  process. 
Extending  obliquely  downwards  and  outwards,  from  the  middle 
of  the  clavicle,  is  a  groove,  marking  the  separation  between  the 
contiguous  borders  of  the  deltoid  and  pectoralis  major,  and  in 
which  may,  by  deep  pressure,  be  felt  the  coracoid  process. 
Another  groove,  passing  outwards  from  the  sterno-clavicular 
joint,  indicates  the  interval  between  the  sternal  and  clavicular 
attachments  of  the  pectoralis  major.  The  upper  arm  below  the 
acromion  is  rounded,  the  convexity  being  caused  by  the  greater 
and  lesser  tuberosities  of  the  humerus.  In  the  more  common 
forms  of  dislocations  of  the  humerus,  this  roundness  is  lost,  and 
a  depression  takes  its  place.  Between  the  thorax  and  the  arm 
there  is  a  deep  hollow  —  the  axilla —  which  varies  according  to 
the  position  of  the  arm  to  the  side.  Its  front  border  is  formed 
by  the  pectoralis  major,  and  its  hinder  border  by  the  latissimus 
dorsi ;  and  if  the  fingers  be  pushed  up  into  this  space,  the  head 
of  the  humerus  can  easily  be  felt.  The  free  border  of  the  pec- 
toralis major  muscle  corresponds  with  the  fifth  rib,  and  below 
this  can  be  distinguished  the  lower  digitations  of  the  serratus 
magnus  with  the  external  oblique. 


308  DISSECTION. 

Dissection. — The  student  must  now  make  three  incisions 
through  the  skin  ;  the  first,  along  the  middle  of  the  whole  length 
of  the  sternum  ;  the  second,  along  the  lower  border  of  the  clav- 
icle, and  down  along  the  front  of  the  upper  arm  for  four  inches 
(10  cm)  ;  the  third,  from  the  ensiform  cartilage,  backwards  to 
the  posterior  border  of  the  axilla. 

The  skin  should  now  be  taken  up  with  the  forceps  at  the 
upper  and  inner  angle,  and  when  the  skin  has  been  so  far  re- 
flected as  to  enable  the  fingers  to  take  it  up,  lay  aside  the  for- 
ceps and  use  the  fingers  in  their  place.  The  skin  should  be 
carefully  dissected  from  the  subjacent  layer  of  subcutaneous 
fascia  and  fat.  In  doing  so,  notice  the  thin,  pale  fibres  of  the 
broad  subcutaneous  muscle  of  the  neck — platysma  viyoides 
(Fig.  14,  p.  43). 

Beneath  this  subcutaneous  fascia  and  fat  there  is  a  strong 
deep  fascia  which  closely  invests  the  muscles,  and  in  the  axilla 
it  forms  a  dense  fascia  which  passes  from  the  pectoralis  major 
to  the  latissimus  dorsi. 

Cutaneous  Nerves. — The  numerous  nerves  which  run  through  the  subcuta- 
neous tissue  of  the  skin  and  mammary  gland  must  be  carefully  dissected  out. 
They  are  derived  from  various  sources ;  some,  branches  of  the  superficial  cervical 
plexus,  descend  over  the  clavicle  ;  others,  branches  of  the  intercostal  nerves,  come 
through  the  intercostal  spaces  close  to  the  sternum,  each  with  a  small  arterj';  a 
third  series,  also  branches  of  the  intercostal  nerves,  come  out  on  the  side  of  the 
chest  and  nin  forwards  over  the  outer  border  of  the  pectoralis  major. 

The  siip}-a-clavictilar  nerves,  which  arise  from  the  third  and  fourth  cervical 
nerves,  descend  over  the  clavicle,  and  are  subdivided,  according  to  their  direction, 
into  sternal,  clavicular,  and  acromial  branches  (Fig.  32,  p.  80).  The  inner  or 
slernal  cross  the  inner  end  of  the  clavicle  to  supply  the  skin  over  the  upper  part  of 
the  sternum.  The  middle  or  clavicular  pass  over  the  middle  of  the  clavicle  and 
supply  the  integument  over  the  front  of  the  chest  and  the  mammary  gland.  The 
outer  or  ac?-omial  branches  cross  over  the  outer  end  of  the  clavicle  and  distribute 
their  filaments  to  the  skin  of  the  shoulder. 

Near  the  sternum  are  found  the  anterior  cutaneous  branches  or  terminal  filaments 
of  the  intercostal  nerves.  After  piercing  the  internal  intercostal  and  pettoralis 
major  muscles  each  nerve  sends  an  inner  filament  to  the  skin  over  the  sternum, 
and  an  outer  larger  one,  which  supplies  the  skin  over  the  pectoral  muscle.  Those 
of  the  third  and  fourth  intercostal  supply  also  the  mammary  gland. 

Branches  of  the  internal  mammary  artery,  for  the  supply  of  the  mammary 
gland,  accompany  these  nerves.  During  lactation  they  increase  in  size,  ramifying 
tortuously  over  the  surface  of  the  gland.  They  are  occasionally  as  large  as  the 
radial  at  the  wrist. 

The  lateral  cutaneous  branches  of  the  intercostal  nerves  come  out  between  the 
digitations  of  the  serratus  magnus  on  the  side  of  the  chest,  and  divide  into  ante- 
rior and  posterior  branches.  The  anterior  branches  curve  round  the  free  border 
of  the  pectoralis  major,  and  then  supnlv  the  skin  over  that  muscle  and  the  mamma. 
The  posterior  liranches  supply  the  skin  of  the  back  of  the  chest. 

Dissection, — Dissect  off  the  superficial  fascia  and  fat  with 
the  mammary  gland.     Thus   you   will   expose  the   strong    deep 


PECTORALIS    MAJOR.  309 

fascia,  which  is  closely  attached  to  the  pectoralis  major  and 
deltoid  muscles.  It  is  continuous,  above,  with  the  fascia  of 
the  neck ;  below,  with  that  of  the  arm.  At  the  axilla  it  be- 
comes denser,  where  it  passes  from  the  pectoral  to  the  latissimus 
dorsi  muscles. 

Reflect  this  fascia  from  the  pectoralis  major  by  dissecting 
parallel  with  the  course  of  its  fibres.  The  muscle  having  been 
fully  exposed,  observe  its  shape,  the  course  of  its  fibres,  their 
origin,  and  insertion.* 

Pectoralis  Major.  —  The  pectoralis  major  is  the  large  tri- 
angular muscle  in  the  front  of  the  chest.  It  arises  from  the 
anterior  surface  of  the  sternal  half  of  the  clavicle,  from  the 
front  of  its  own  half  of  the  sternum,  from  the  cartilages  of  all 
the  true  ribs  except  the  last,  and  from  the  aponeurosis  of  the 
external  oblique  muscle  of  the  abdomen.  From  this  extensive 
origin  the  fibres  converge  towards  the  arm,  the  upper  ones 
passing  downwards  and  outwards,  the  middle  ones  transversely 
outwards,  and  the  lower  fibres  upwards  and  outwards  ;  they 
terminate  in  a  flat  tendon,  about  two  inches  in  breadth,  which 
is  ifiscrtcd  into  the  anterior  margin  of  the  bicipital  groove  of 
the  humerus.  The  arrangement  of  its  fibres,  as  well  as  the 
structure  of  its  tendon,  is  peculiar — on  vertical  cross  section 
is  U  shape.  The  lower  fibres,  which  form  the  boundary  of  the 
axilla,  are  folded  beneath  the  rest,  and  terminate  upon  the 
upper  part  of  the  tendon  —  z>.,  nearer  to  the  shoulder-joint; 
the  upper  fibres,  which  arise  from  the  clavicle,  and  are  fre- 
quently separated  from  the  main  body  of  the  muscle  by  a  slight 
interval,  descend  in  front  of  the  lower  and  terminate  upon  the 
lower  part  of  the  tendon.  Consequently  the  upper  and  lower 
fibres  of  the  muscles  cross  each  other  previously  to  their  in- 
sertion (Fig.  120,  p.  316). 

The  object  of  this  arrangement  is  to  enable  all  the  fibres  to 
act  simultaneously  when  the  arm  is  extended. 

The  upper  part  of  the  tendon  sends  off  a  fibrous  prolonga- 
tion, which  binds  down  the  long  head  of  the  biceps,  and  is 
attached  to  the  great  tuberosity  of  the  humerus ;  another  ten- 
dinous expansion  is  prolonged  backwards  to  the  tendon  of  the 
deltoid  muscle ;  and  a  third  passes  downwards  to  be  intimately 
connected  with  the  fascia  of  the  upper  arm. 

*  Sometimes  we  find  a  thin  little  muscle  running  peipendicularly  in  front  of 
the  inner  part  of  the  pectoralis  major.  This  is  the  7ectus  sterualis,  ox  siernalis 
brtiioriim.  It  arises  infeiiorly  by  a  tendinous  expansion  fioni  the  rectus  abdom- 
inis, and  is  connected  above  to  the  tendon  of  the  s'erno  mastoid. 


310 


COSTO-CORACOID    MEMBRANE. 


The  chief  actioji  of  the  pectorahs  major  is  to  draw  the 
humerus  towards  the  chest,  as  in  placing  the  hand  on  the  oppo- 
site shoulder,  or  in  pulHng  an  object  towards  the  body.  When 
the  arm  is  raised  and  made  the  fixed  point  the  muscle  assists  in 
raising  the  trunk,  as  in  climbing.  Thus,  too,  on  emergency,  it 
can  act  as  an  auxiliary  muscle  of  inspiration. 

Between  the  pectoralis  major  and  the  deltoid,  the  great 
muscle  covering  the  shoulder,  is  an  interval  varying  in  extent 
in  different  subjects,  but  always  more  marked  towards  the 
clavicle.  It  contains  a  small  artery  —  the  tJioracica  Jimneraria 
—  and  the  cephalic  vein,  which  ascends  on  the  outer  side  of  the 
arm  and  empties  itself  into  the  axillary.  This  interval  is  the 
proper  place  to  feel  for  the  coracoid  process.  In  doubtful  in- 
juries about  the  shoulder  this  point  of  bone  is  a  good  landmark 
in  helping  the  surgeon  to  arrive  at  a  correct  diagnosis. 

The  pectoralis  major  is  supplied  with  7ierves  by  the  external 
anterior  thoracic  and  some  filaments  from  the  internal  anterior 
thoracic  branches  of  the  brachial  plexus  ;  with  blood,  by  the 
long  and  short  thoracic  branches  of  the  axillary  artery. 

Dissection.  Anatomy  of  the  Infra-clavicular  Region. — 
Reflect  the  clavicular  part  of  the  pectoralis  major  by  detaching 
it  from  the  clavicle,  and  turn  it  downwards  ;  in  doing  so,  notice 
a  small  nerve,  the  external  anterior  thoracic,  which  enters  the 
under  surface  of  this  part  of  the  muscle.  Beneath  the  portion 
thus  reflected,  part  of  the  pectoralis  minor  will  be  exposed.  In 
this  triangle  —  bounded,  above,  by  the  clavicle;  below,  by  the 
upper  border  of  the  sternal  origin  of  the  pectoralis  major  ;  and, 
on  the  outer  side,  by  the  deltoid  —  is  an  important  space  in 
which  the  relative  position  of  the  following  objects  must  be 
carefully  examined  :  — 

Costo-coracoid  Membrane.  —  a.  A  strong  ligamentous  ex- 
pansion, called  the  costo-coracoid  vicmbrajie  or  clavi-pcctoral 
fascia,  extends  from  the  cartilage  of  the  first  rib  to  the  cora- 
coid process.  Between  these  points  it  is  attached  to  the  clavi- 
cle, and  forms  a  complete  investment  for  the  subclavius  muscle.* 
Its  lower  crescent-shaped  edge  arches  over,  and  protects  the 
axillary  vessels  and  nerv^es  ;  from  this  edge  is  prolonged  down- 
wards a  funnel-shaped  fascia,  which  covers  the  axillary  vessels, 

*  This  fascia  extends  to  the  cephalad  or  superior  border  of  the  pectoralis 
minor  muscle;  the  fascia  then  divides  into  three  layers,  the  ventral  or  anterior  two 
surrounding  the  muscle,  and  finally  being  lost  in  the  axillary  fascia ;  the  dorsal 
or  posterior  layer  being  lost  on  the  vessels.  — A.  II. 


AXILLARY    VESSELS    AND    NERVES.  3II 

forming  the  anterior  portion  of  their  sheath,  the  posterior  being 
formed  by  a  prolongation  of  the  deep  cervical  fascia.  The 
front  portion  of  this  sheath  is  perforated  by  the  cephalic  vein, 
the  thoracica  acromialis  artery  and  vein,  the  anterior  thoracic 
nerves,  and  the  superior  thoracic  artery.  This  fascia  must  be 
removed. 

b.  The  subclavius  muscle  enclosed  in  its  fibrous  sheath. 

c.  The  axillary  vein,  artery,  and  brachial  plexus  of  nerves. 

d.  Two  arteries,  the  superior  or  short  thoracic  and  the  tho- 
racica acromialis. 

e.  The  termination  of  the  cephalic  vein  in  the  axillary. 

f.  Two  nerves,  the  external  and  internal  anterior  thoracic, 
which  descend  from  the  brachial  plexus  below  the  clavicle,  and 
cross  in  front  of  the  axillary  vessels  to  supply  the  pectoral 
muscles. 

Subclavius. — This  muscle  lies  between  the  clavicle  and  the 
first  rib.  It  arises  from  the  first  rib  by  a  short  round  tendon 
at  the  junction  of  the  bone  and  cartilage  in  front  of  the  costo- 
clavicular ligament,  and  is  inserted  into  the  groove  on  the  under 
surface  of  the  clavicle  as  far  outwards  as  the  coraco-clavicular 
ligament.  Its  nerve  comes  from  the  fifth  and  sixth  cervical 
nerves.  Its  action  is  to  depress  the  clavicle,  and  prevent  its 
too  great  elevation  (Fig.  120,  p.  316). 

Relative  Position  of  the  Axillary  Vessels  and  Nerves. 
—  In  the  infra-clavicular  space  before  us  are  the  great  vessels 
and  nerves  of  the  axilla  in  the  first  part  of  their  course.  They 
lie  at  a  great  depth  from  the  surface.  They  are  surrounded  by 
a  sheath  of  fascia,  which  descends  with  them  beneath  the  clav- 
icle. Their  relations  with  regard  to  each  other  are  as  follows  : 
The  axillary  vein  lies  in  front  of  the  artery,  and  rather  to  its 
thoracic  side.  The  brachial  plexus  of  nerves  is  situated  above 
the  artery,  and  on  a  posterior  plane.  The  plexus  consists  of 
two,  or  sometimes  three,  large  cords,  which  result  from  the 
union  of  the  anterior  branches  of  the  four  lower  cervical,  and 
the  first  thoracic  nerves.  The  course  and  relations  of  the  axil- 
lary artery  will  be  examined  subsequently. 

Superior  Thoracic  and  Acromio-Thoracic  Arteries.  — 
These  are  two  branches  which  arise  from  the  axillary  artery  in 
the  first  part  of  its  course,  above  the  pectoralis  minor.  The 
superior  thoracic  frequently  arises  in  common  with  the  acromio- 
thoracic,  and  passing  along  the  upper  border  of  the  pectoralis 
minor,  descends  between  this  muscle  and  the  pectoralis  major. 


312  ANTERIOR    THORACIC    NERVES. 

supplying  both,  and  anastomosing  with  the  intercostal  and  inter- 
nal mammary  arteries.  The  thoracica  acroniialis  is  given  off 
just  above  the  pectoralis  minor,  and  shortly  divides  into  three 
sets  of  branches  :  viz.,  two  or  three  small  thoracic  branches  to 
the  serratus  magnus  and  pectoral  muscles ;  the  tJioracica  Jmme- 
raria,  which  descends  with  the  cephalic  vein,  in  the  interval  be- 
tween the  pectoralis  major  and  deltoid,  and  ramifies  in  both  ; 
and  lastly,  the  acromial  brancJi,  which  passes  over  the  coracoid 
process  to  the  under  surface  of  the  deltoid,  which  it  supplies, 
and  communicates  with  the  posterior  circumflex,  a  branch  of 
the  axillary,  and  the  supra-scapular,  a  branch  of  the  subclavian. 
A  constant  though  small  branch,  the  clavicular,  runs  along  the 
anterior  aspect  of  the  subclavius.  All  these  arteries  are  accom- 
panied by  veins,  which  most  frequently  empty  themselves  into 
the  cephalic,  but  occasionally  into  the  axillary  vein. 

Cephalic  Vein.  —  The  cephalic  vein  is  one  of  the  principal 
cutaneous  veins  of  the  arm.  Commencing  on  the  back  of  the 
thumb  and  forefinger,  it  runs  up  the  radial  side  of  the  forearm, 
in  front  of  the  elbow-joint ;  thence  ascending  along  the  outer 
edge  of  the  biceps,  it  runs  up  the  interval  between  the  pectoralis 
major  and  deltoid,  pierces  the  costo-coracoid  membrane,  crosses 
over  the  axillary  artery,  and  finally  empties  itself  into  the  ax- 
illary vein.* 

Anterior  Thoracic  Nerves.  —  These  nerves  come  from 
the  brachial  plexus  below  the  clavicle  to  supply  the  pectoral 
muscles.  There  are  generally  two  —  an  external  and  an  inter- 
nal -—  one  for  each  pectoral  muscle.  The  external,  the  more 
superficial,  arises  from  the  outer  cord  of  the  brachial  plexus, 
passes  over  the  axillary  artery  and  vein,  pierces  the  costo-cora- 
coid membrane,  and  supplies  the  pectoralis  major  on  its  under 
aspect :  it  communicates  with  the  next  nerve  by  a  filament 
which  forms  a  loop  on  the  inner  side  of  the  artery  ;  the  inter- 
nal, and  smaller  branch,  comes  from  the  internal  cord,  and  de- 
scends between  the  axillary  artery  and  vein  {occasionally  through 
the  vein)  to  supply  the  pectoralis  minor  on  its  under  surface, 
some  of  its  filaments  passing  through  this  muscle  to  the  pecto- 
ralis major. 

Difficulty  of  Tying  the  First  Part  of  the  Axillary  Ar- 
tery.—  From  this  view  of  the  relations  of  the  axillary  artery  in 

*  The  cephalic  vein,  in  some  cases,  runs  over  the  clavicle  to  join  the  eoiternal 
jugular;  or  there  may  be  a  communication  (termed  jugulo-cephalic)  between  these 
veins. 


DISSECTION    OF    THE    AXILLA.  313 

ihe  first  part  of  its  course,  some  idea  may  be  formed  of  the  dif- 
ficulty of  passing  a  ligature  round  it  in  this  situation.  In  addi- 
tion to  its  great  depth  from  the  surface,  varieties  sometimes 
occur  in  the  position  of  the  nerves  and  veins,  which  render  the 
operation  still  more  embarrassing.  For  instance,  the  anterior 
thoracic  nerves  may  be  more  numerous  than  usual,  and  form 
by  their  mutual  communication  a  plexus  around  the  artery.  A 
l^rge  nerve  is  often  seen  crossing  obliquely  over  the  artery, 
immediately  below  the  clavicle,  to  form  one  of  the  roots  of  the 
median  nerve.  The  cephalic  vein  may  ascend  higher  than 
usual,  and  open  into  the  subclavian;  and  as  it  receives  large 
veins  corresponding  to  the  thoracic  axis,  a  concourse  of  veins 
would  be  met  with  in  front  of  the  artery.  Again,  it  is  by  no 
means  uncommon  to  find  a  deep-seated  vein,  the  supra-scapular, 
crossing  over  the  artery  to  join  the  axillary  vein. 


DISSECTION   OF  THE  AXILLA. 

Sebaceous  Glands.  —  On  the  under  surface  of  the  skin  of 
the  axilla,  near  the  roots  of  the  hairs,  are  numerous  sebaceous 
glands.  They  are  of  a  reddish-brown  color,  and  rather  larger 
than  a  pin's  head. 

Axillary  Fascia.  —  This  dense  fascia,  which  lies  immedi- 
ately beneath  the  skin  of  the  axilla,  is  a  continuation  of  the 
general  fascial  investment  of  the  muscles.  It  closes  in  and 
forms  the  floor  of  the  cavity  of  the  axilla.  Externally,  it  is 
strengthened  by  fibres  from  the  tendons  of  the  pectoralis  major 
and  latissimus  dorsi,  and  is  continuous  with  the  fascia  of  the 
arm  ;  internally,  it  is  prolonged  on  the  side  of  the  chest,  over 
the  serratus  magnus  muscle  ;  in  front  and  behind,  it  divides,  so 
as  to  enclose  between  its  layers  the  muscles  which  form  the 
boundaries  of  the  axilla.  Thus  the  anterior  layer  encloses  the 
two  pectoral  muscles,  and  is  connected  with  the  coracoid  pro- 
cess, the  costo-coracoid  ligament,  and  the  clavicle ;  the  posterior 
layer  encloses  the  latissimus  dorsi,  and  passes  backwards  to  the 
spine. 

A  subcutaneous  artery,  sometimes  of  considerable  size,  is 
often  found  in  the  substance  of  the  axillary  fascia.  It  gener- 
ally arises  from  the  brachial,  or  from  the  lower  part  of  the  axil- 
lary artery,  and  runs  across  the  floor  of  the  axilla  towards  the 
lower  edge  of  the  pectoralis  major.      It  is  not  a  named  branch, 


314  BOUNDARIES    OF    THE    AXILLA. 

but  should  be  remembered,  as  it  would  occasion  much  hemor- 
rhage if  wounded  in  opening  an  abscess. 

Dissection  and  Contents  of  the  Axilla.  —  Reflect  the 
axillary  fascia,  to  display  the  boundaries  and  the  contents  of  the 
axilla.  The  dissection  of  this  space  is  difficult,  and  must  be 
done  cautiously.  Bear  in  mind  that  the  trunk  blood-vessels  and 
nerves  run  through  the  tipper  2ind  <??//rr  part  of  the  axilla;  that 
the  long  thoracic  artery  runs  along  the  anterior  border,  and  the 
subscapular  artery  along  the  posterior.  Commence  dissecting,- 
therefore,  in  the  middle  ;  break  down  with  the  handle  of  the 
scalpel  the  loose  connective  tissue,  fat,  and  lymphatic  glands, 
which  occupy  the  cavity.  You  will  soon  discover  some  cuta- 
neous nerves  coming  out  between  the  ribs,  and  then  crossing 
the  axillary  space.  These  nerves  are  the  posterior  lateral  cuta- 
neous bj-anclies  of  the  intercostal  nerves ;  they  perforate  the 
intercostal  spaces  between  the  digitations  of  the  serratus  mag- 
nus,  midway  between  the  sternum  and  the  spine,  and  divide 
into  anterior  and  posterior  branches.  The  anterior  turn  over 
the  pectoralis  major,  to  supply  the  skin  on  the  front  of  the 
chest  and  the  mammary  gland.  The  posterior  pass  backwards 
over  the  latissimus  dorsi,  and  are  distributed  to  the  skin  cover- 
ing this  muscle  and  the  scapula. 

Intercosto-humeral  Nerves. — The  posterior  lateral  branch 
of  the  second  intercostal  nerve  requires  a  special  description. 
It  is  larger  than  the  others,  and  is  called  the  intercosto-Immeral, 
because  it  supplies  the  integuments  of  the  arm.  It  comes 
through  the  second  intercostal  space,  traverses  the  upper  part 
of  the  axilla,  where  it  receives  a  branch  of  the  lesser  internal 
cutaneous  nerve  (nerve  of  Wrisberg),  and,  piercing  the  fascia, 
terminates  in  filaments,  which  are  distributed  to  the  skin  on  the 
inner  side  and  back  of  the  arm,  as  low  as  the  internal  condyle. 
The  corresponding  branch  of  the  third  intercostal  is  also  an 
intcrcosto-Jinmeral  nerve.  It  receives  a  branch  from  the  second, 
and  runs  a  similar  course.  The  distribution  of  these  nerves* 
accounts  for  the  pain  down  the  arm  which  is  sometimes  experi- 
enced in  ]ileurisy. 

Boundaries  of  the  Axilla. — -The  axilla  is  a  conical  space, 
of  which  the  apex  is  beneath  the  clavicle,  and  the  base  between 
the  pectoralis  major  and  the  latissimus  dorsi.  Obviously  it 
varies  in  capacity  according  to  the  position  of  the  arm  to  the 

*  In  carcinoma  of  the  breast,  pain  is  transmitted  to  the  elbow  when  the  deep 
lymphatics  and  the  muscles  are  invaded. 


AXILLARY    LYMPHATIC    GLANDS. 


315 


side.  On  the  inner  side,  it  is  bounded  by  the  four  upper  ribs, 
with  their  corresponding  intercostal  muscles  and  the  serratus 
magnus  ;  on  the  outer,  by  the  humerus,  covered  by  the  coraco- 
brachialis  and  biceps  ;  in  front,  by  the  pectoralis  major  and 
minor;  behind,  by  the  latissimus  dorsi,  teres  major,  and  sub- 
scapularis.  Its  anterior  and  posterior  boundaries  converge  from 
the  chest,  so  that  the  axilla  becomes  narrower  towards  the  arm. 
With  a  full  view  of  the  axilla  before  you,  bear  in  mind  that  pus 


Fig.   iig.  —  Thoracic  and  Brachial    Lymphatic  Vi -^-^els  emptying   into  the  Axillary 

LvMi'HAric   Glanus. 


may  burrow  under  the  pectoral  muscles,  or  under  the  scapula, 
or  that  it  may  run  up  beneath  the  clavicle  and  point  in  the 
neck,  if  the  abscess  be  allowed  to  remain  unopened  (Fig.  120). 
Axillary  Lymphatic  Glands.  —  The  axillary  glands  form  a 
continuous  chain,  beneath  the  clavicle,  with  the  cervical  glands. 
They  are  from  ten  to  twelve  in  number,  of  a  reddish-brown 
color,    and   variable  size.      Most  of  them  lie  near  the  axillary 


3i6 


PECTORAL  IS    MINOR. 


vessels  ;  others  are  embedded  in  the  loose  tissue  of  the  axilla  ; 
sometimes  one  or  two  small  ones  ar-e  observed  along  the  lower 
border  of  the  pectoralis  major.  They  are  supplied  with  blood 
by  a  branch  —  tJioracica  alaiis  —  of  the  axillary  artery,  and  by 
branches  from  the  thoracic  and  subscapular  arteries  (Fig.  1 19). 
These  glands  receive  the  lymphatics  from  the  arm,  from  the 
front  and  side  of  the  chest,  and  from  the  outer  half  of  the  mam- 
mary gland.  It  is  these  glands  which  become  enlarged  in  can- 
cer of  the  mammary  gland.     From  these  glands  the  efferent 


10  11 

Fig.  120. — Muscles  of  the  Anterior  Part  of  the  Thorax. 

I.  Pectoralis  major.  2.  Its  cla\'icular  portion.  3.  Its  sternal  portion.  4.  Cut  portion  of  the 
whole  muscle  deflected  to  show  the  long  head  of  the  biceps,  showing  also  the  turning  of  the 
fibres  of  the  muscle  before  their  insertion.  5.  Muscular  fasciculi  by  which  the  pectoralis 
major  arises  from  the  costal  cartilages.  6.  Pectoralis  minor  m.  7.  Subclavius  m.  S.  Deltoid 
m.,  separated  from  the  superior  border  of  the  pectoralis  major  by  a  wedge-sliaped  cellular  inter- 
space, the  base  being  above.  9.  Inferior  border  of  the  pectoralis  minor.  10.  L)igitations  of 
the  serratus  magnus  m.  11.  Digitations  of  the  external  oblique  m.  12.  Border  of  the  latissimus 
dorsi  ra.  13.  Tendon  of  this  muscle  passing  around  the  teres  major  m.tobe  attached  to  the 
inner  lip  of  the  bicioital  groove  of  the  humerus.  14.  Teres  major  m.  15.  Subscapularis  m. 
16.  Long  head  of  the  triceps  m.  17.  Margin  of  deltoid  m.  18.  Stemo-cleido-mastoid  m. 
19.  Origin  of  sterno-hyoideus  m.     20.  Trapezius  m. 

lymphatics  pass  along  with  the  subclavian  artery  and  terminate, 
on  the  right  side,  in  the  right  lymphatic  duct ;  and,  on  the  left 
side,  in  the  thoracic  duct. 

Dissection.  —  Now  cut  through  the  pectoralis  major,  about 
the  middle,  and  turn  the  inner  part  of  the  muscle  towards  the 
sternum,  and  the  outer  part  towards  the  arm.  The  pectoralis 
minor  is  thus  exposed,  together  with  the  ramifications  of  the 
short  and  long  thoracic  arteries.  Preserve  the  arteries,  as  far 
as  possible,  in  connection  with  the  main  trunks. 

Pectoralis  Minor.  —  This  triangular  muscle  arises  from  the 
third,  fourth,  and  fifth  ribs,  near  the  costal  cartilages,  and  from 


AXILLARY    ARTERY.  317 

the  thick  fascia  .over  the  intercostal  spaces.  The  fibres  run 
obHquely  upwards  and  outwards,  and  converge  to  a  strong  ten- 
don, which  is  inserted  into  the  anterior  surface  of  the  coracoid 
process.  The  tendon  is  connected  to  that  of  the  coraco-brachi- 
alis  and  biceps  by  a  strong  fascia,  which  forms  a  protection  for 
the  subjacent  axillary  vessels  and  nerves.  The  action  of  this 
muscle  is  to  draw  the  scapula  downwards  and  forwards.  Its 
nerve  is  derived  from  the  internal  anterior  thoracic. 

Dissection.  —  Having  examined  the  muscles  which  form  the 
anterior  boundary  of  the  axilla,  we  pass  now  to  the  course  and 
relations  of  the  axillary  artery  and  its  branches.  To  have  a 
clear  view,  reflect  the  subclavius  from  its  insertion,  and  cut  the 
pectoralis  minor  through  its  middle. 

Axillary  Artery,  its  Course  and  Relations.  —  This  artery, 
the  continuation  of  the  subclavian,  takes  the  name  of  axillary 
at  the  outer  border  of  the  first  rib.  It  then  passes  downwards 
and  outwards,  through  the  upper  part  of  the  axilla,  beneath  the 
two  pectoral  muscles,  and  along  the  inner  border  of  the  coraco- 
brachialis  as  far  as  the  lower  border  of  the  tendon  of  the  teres 
major,  beyond  which  it  is  continued  under  the  name  of  the 
brachial.  Its  course  is  divided  for  convenience  of  description 
into  three  parts :  the  first  lies  above  the  pectoralis  minor ;  the 
second  behind  that  muscle  ;  and  the  third  below  it. 

In  the  first  part  of  its  course  the  artery  is  covered  by  the 
pectoralis  major  and  the  costo-coracoid  membrane,  the  sub- 
clavius, and  is  crossed  by  the  cephalic  and  acromio-thoracic 
veins.  On  its  inner  side,  and  slightly  in  front,  is  the  axillary 
vein;  on  its  outer  side  is  the  brachial  plexus  of  nerves;  behind 
it  are  the  first  intercostal  space,  the  second  digitation  of  the 
serratus  magnus,  and  the  posterior  thoracic  nerve  (external 
respiratory  of  Bell). 

In  the  second  part  of  its  course  it  lies  behind  the  pectoralis 
major  and  minor  ;  on  its  ittner  side  is  the  axillary  vein,  still 
slightly  anterior,  but  separated  from  the  artery  by  the  inner 
cord  of  the  brachial  plexus  ;  on  its  outer  side  is  the  outer  cord 
of  the  brachial  plexus  ;  and  behind  it  is  the  posterior  cord  of 
the  plexus,  and  also  a  quantity  of  loose  connective  tissue  which 
separates  it  from  the  subscapularis  muscle.  The  inner  head  of 
the  median  nerve  is  often  in  front  of  the  artery  in  this  part  of 
its  course. 

In  the  third  part,  in  front  of  the  artery,  are  the  pectoralis 
major,  the  two  roots  of  the  median  nerve,  converging  like  the 


3i8 


BRANCHES    OF    THE    AXILLARY    ARTERY. 


letter  V,  find  lower  down  is  the  skin  and  the  fascia  of  the  arm  ; 
on  the  outer  side  are  the  coraco-brachialis,  the  musculo-cutane- 
ous,  and  median  nerves ;  on  the  inner  side  are  the  axillary  vein, 
the  ulnar,  and  the  two  internal  cutaneous  nerves  ;  bcJiind  it  are, 
in  succession,  the  subscapularis,  the  latissimus  dorsi,  the  teres 
major,  and  the  musculo-spiral  and  circumflex  nerves. 


Fig.  121.  —  Diagram  of  Axit.i.a. 

Axillary  artery.  2.  Brachial  artery.  3.  Thoracica  humeraria  artery.  4-  Superior  thoracic 
artery.  5.  .Subscapular  artery.  6.  Uorsalis  scapulae  artery.  7.  Posterior  circumflex  artery. 
8.  Superior  profunda  artery,  g.  Posterior  thoracic  nerve.  10.  Long  subscapular  nerve. 
II.  Median  nerve.     12.  Cephalic  vein.     13.  Musculo-cutaneous  nerve.     14-  Teres  major. 


Branches  of  the  Axillary  Artery.  —  The  number  and  ori- 
gin of  these  branches  often  vary,  but  their  general  course  is  in 
most  cases  similar,  and  they  usually  arise  in  the  following 
order : — 


BRANCHES    OF    THE    AXILLARY    ARTERY. 


319 


a.  The  superior  or  short  thoracic  arises  above  the  pectoraHs  minor,  and  divides 
into  branches,  which  have  been  already  described  (p.  311). 

b.  The  acromial  thoracic  also  rises  above  the  pectoralis  minor,  and  gives  off 
numerous  branches  already  described  (p.  311). 

c.  The  alar  thoracic,  variable  in  its  origin,  supplies  the  lymphatic  glands  and 
the  connective  tissue  of  the  axilla. 

d.  The  inferior  or  long  thoracic  artery  (external  mammary)  runs  along  ihe 
lower  border  of  the  pectoralis  minor  to  the  side  of  the  chest.  It  supplies  the 
mammary  gland,  the  serratus  magnus  and  pectoral  muscles,  and  maintains  a  free 
anastomosis  with  the  short  thoracic,  internal  mammary,  and  intercostal  arteries. 

e.  The  subscapular  is  the  largest  branch  of  the  axillary ;  it  arises  opposite  the 
lower  border  of  the  subscapularis,  and,  after  running  a  short  course  of  about  an 
inch  and  a  half  {^.S  cm.),  divides  into  an  anterior  and  posterior  branch. 

The  anterior  branch  runs  along  the  anterior  edge  of  the  subscapularis  towards 
the  lower  angle  of  the  scapula.  Its  numerous  branches  supply  the  subscapularis, 
latissimus  dorsi,  serratus  magnus,  and  teres  major,  and  anastomose  with  the  inter- 
costal and  thoracic  arteries,  and  with  the  posterior  scapular  (a  branch  of  the  sub- 
clavian). 


Fig.  122. — Plan  of  the  Branches  of  the 

Axillary  Artery. 
.  Thoracic  axis,  giving  off.  2.  .Short  thoracic. 
3.  Thoracica  acromialis.  4.  Thoracica  hume- 
raria.  5.  Long  thoracic.  6.  Subscapular.  7. 
DorsaHs  scapuls.  8.  Anterior  circumflex.  9. 
Posterior  circumflex. 


Fig.  123.  — Diagram  of  the  Ori- 
gins OF  THE  Triceps. 

I.  Subscapularis.  2.  Teres  major. 
3.  Long  head  of  triceps.  4.  Square 
space  for  post,  circumflex  a.  and 
n .  5 .  Triangular  space  for  dorsalis 
scapulsn.  6.  Spacefor  musculo- 
spiral  n.,and  superior  profunda  a. 


The  posterior  branch  (dorsalis  scapulse)  runs  to  the  back  of  the  scapula, 
through  a  triangular  space,  bounded  in  front  by  the  long  head  of  the  triceps; 
below,  by  the  teres  major;  and,  above,  by  the  subscapularis  and  teres  minor 
(Fig.  123).  It  gives  off  a  small  branch  which  enters  the  subscapular  fossa  be- 
neath the  subscapularis,  supplying  it,  and  anastomosing  with  the  suprascapular 
and  posterior  scapular  arteries.  On  the  back  of  the  scapula  it  divides  into  two 
branches:  one  runs  in  the  groove  on  the  axillary  border  of  the  scapula,  lying  be- 
neath the  teres  minor,  and  ramifies  in  the  infraspinous  fossa  between  the  bo-e 
and  the  infraspinatus;  the  other  runs  down  between  the  teres  minor  and  major 
on  their  dorsal  aspects,  and  passes  to  the  inferior  angle  of  the  scapula,  anas' o- 
mosing  with  the  posterior  and  suprascapular  arteries.  The  subscapular  vein 
empties  itself  into  the  axillary  vein. 

/.  The  posterior  circumflex  artery  arises  from  the  back  of  the  ax'llary  Prtery, 
and  is  as  large  as  the  subscapular,  close  to  which  it  is  given  off;   or  Loth  may 


320  AXILLARY    VEIN. 

arise  by  a  common  trunk  from  the  axillary.  It  passes  oackwards,  with  its  cor- 
responding veins  and  nerve,  through  a  quadrilateral  space,  bounded  above  by  the 
subscapularis  and  teres  minor,  below  by  the  teres  major,  externally  by  the  neck 
of  the  humerus,  and  internally  by  the  long  head  of  the  triceps  (Fig.  123).  It 
then  winds  round  the  back  of  the  neck  of  the  humerus,  and  is  chiefly  distributed 
to  the  under  surface  of  the  deltoid. 

Besides  the  deltoid,  the  posterior  circumflex  artery  supplies  the  long  head  of 
the  triceps,  the  head  of  the  humerus,  and  the  shoulder-joint.  It  inosculates  above 
with  the  acromio-thoracic  and  suprascapular  arteries,  below  with  the  ascending 
branch  of  the  superior  profunda  (a  branch  of  the  brachial),  and  in  front  with  tie 
anterior  circumflex  artery.  Should  you  not  find  the  posterior  superior  circumflex 
artery  in  its  nonnal  position,  look  for  it  (as  a  branch  of  the  brachial)  below  the 
tendon  of  the  teres  major. 

g.  The  anterior  circtanflcx  artery,  much  smaller  than  the  posterior,  runs  in 
front  of  the  neck  of  the  humerus,  above  the  tendon  of  the  latissimus  dorsi.  It 
passes  directly  outwards  beneath  the  coraco-brachialis  and  short  head  of  the 
biceps,  close  to  the  bone,  and  terminates  in  the  under  surface  of  the  deltoid, 
where  it  inosculates  with  the  posterior  circumflex. 

The  anterior  circumflex  artery  sends  a  small  branch  which  runs  with  the  long 
tendon  of  the  biceps  up  the  groove  of  the  humerus,  and  is  called,  on  that  ac- 
count, the  bicipital  artery.  It  supplies  the  shoulder-joint  and  the  neck  of  the 
humerus. 

If  the  axillary  were  tied  below  the  pectoralis  minor  the  col- 
lateral circulation  would  be  established  by  the  suprascapu]  r 
and  its  branches  anastomosing  with  the  subscapular,  the  dorsal  is 
scapulae,  and  the  posterior  circumflex ;  the  posterior  scapular 
with  the  dorsalis  scapulae  and  subscapular  arteries.* 

Axillary  Vein.  —  The  axillary  vein  is  formed  by  the  con- 
tinuation upwards  of  the  basilic  vein,  and  extends  from  the 
lower  border  of  the  teres  major  to  the  outer  border  of  the  first 
rib.  It  receives  the  venae  comites  of  the  brachial  artery  near 
the  lower  border  of  the  subscapularis.  It  receives  the  sub- 
scapular and  the  other  veins  corresponding  to  the  branches  of 
the  axillary  artery,  with  the  exception  of  the  circumflex,  which 
usually  join  either  the  subscapular  or  one  of  the  venae  comites. 
The  axillary  near  its  termination  also  receives  the  cephalic 
vein. 

The  axillary  vein  in  the  upper  part  of  its  course  lies  in  front 
of  the  artery,  and  close  to  its  sternal  side  ;  in  the  lower  two- 
thirds  of  its  course  the  vein  lies  still  to  the  sternal  side  of  the 
artery,  but  is  separated  from  it  by  some  of  the  nerves  of  the 
brachial  plexus,  f 

*  The  axillary  artery  varies  much  as  to  the  branches  it  gives  off;  occasionally 
(r  in  33)  it  gives  off  the  radial  artery;  more  rarely  (i  in  72)  it  gives  off  the  ulnar; 
and  more  rarely  .still  (i  in  50^1)  it  gives  off  the  interosseous  artery. 

t  It  must  be  remembered  that  the  size  of  the  axillary  vein  compared  with  the 
brachial  is  very  much  larger,  consequently  the  greater  danger  in  mistaking  it  for 
t!  e  axillary  artery  and  from  puncture  when  the  axilla  has  to  be  opened.  —  A.  H. 


BRACHIAL  PLEXUS  OF  NERVES.  321 

Axillary  or  Brachial  Plexus  of  Nerves.  —  This  plexus  is 
formed  by  the  anterior  trunks  of  the  four  lower  cervical  and 
first  thoracic  nerves,  and  receives  also  a  small  communicating 
branch  from  the  fourth  cervical  nerve.  The  plexus  is  broad  at 
the  lower  part  of  the  neck,  where  it  emerges  between  the  an- 
terior and  middle  scalene  muscles  ;  but  it  gradually  contracts 
as  it  descends  beneath  the  clavicle  into  the  axilla,  and  on  a 
level  with  the  coracoid  process  distributes  its  large  branches  to 
the  upper  limb. 

The  arrans:ement  of  the  cervical  nerves  in  the  formation  of 


KiG.  124. — The  Brachial  Plexus  of  Nerves. 

c  4-8.  The  five  lower  cervical  nerves,  d  i.  The  first  thoracic  nerve.  9.  The  rhomboid  nerve — to 
rhomboidei  major  and  minor.  10.  The  supra-scapular  nerve  —  to  supra  and  infra  spinati.  11. 
The  nerve  to  the  subclavius.  12.  External  anterior  thoracic  nerve  —  to  pectoralis  major.  13. 
Internal  anterior  thoracic  nerve  —  to  pectoralis  minor.  14,  15,  16.  The  subscapular  nerves  —  to 
subscapularis,  latissimus  dorsi,  and  teres  major.  17.  Lesser  internal  cutaneous  nerve.  18. 
Musculo-cutaneous  nerve,  ig.  Musculo-spiral  nerve.  20.  Median  nerve.  21.  Circumflex 
nerve  —  to  deltoid  and  teres  minor.  22.  Ulnar  nerve.  23.  Internal  cutaneous  nerve.  24.  Ex- 
ternal respiratory  nerve  of  Bell,  or  posterior  thoracic  nerve. 

the  plexus  is  variable,  often  not  alike  on  both  sides.*  The 
most  frequent  disposition  is  this  —  the  fifth  and  sixth  cervical 
unite  at  the  outer  border  of  the  scalenus  medius  to  form  an  up- 
per cord  ;  the  eighth  and  the  first  thoracic  form  between  the 
scaleni  muscles  a  lower  cord  ;  the  seventh  cervical  runs  alone, 

*  Frequently  the   second   thoracic  nerve   sends  upwards  a  communicating  fila- 
ment to  the  first  thoracic  nerve.  —  [Journal  0/  Anatomy,  vol.  xi.  p.  539.) 


322  BRACHIAL    PLEXUS    OF    NERVES. 

as  a  middle  cord,  for  a  short  distance.  Each  of  these  nerves 
divides,  just  external  to  the  outer  border  of  the  scalenus  medius, 
into  an  anterior  and  a  posterior  branch  ;  the  anterior  branches 
given  off  from  the  fifth,  sixth,  and  seventh  cervical  form  the 
outer  cord  of  the  plexus  ;  the  anterior  branches  given  off  from 
the  eighth  cervical  and  the  first  thoracic  form  the  inner  cord ; 
while  the  posterior  branches  of  all  the  nerves  —  viz.,  the  fifth, 
sixth,  seventh,  eighth  cervical,  and  the  first  thoracic — unite  to 
form  the  posterior  cord. 

At  first  these  cords  are  placed  on  the  outer  side  of  the  axil- 
lary artery,  but  behind  the  pectoralis  minor  they  are  situated 
one  on  the  outer  side  of,  one  on  the  inner  side  of,  and  one  be- 
hind, the  axillary  artery. 

The  brachial  plexus  gives  off  some  branches  above  the 
clavicle,  which  were  dissected  with  the  neck  (p.  137).  Below 
the  clavicle,  it  gives  off  the  following  : — 

From  the  outer  cord  proceed  an  anterior  thoracic  branch,  the 
musculo-cutaneous,  and  the  outer  head  of  the  median  ;  from  the 
inner  cord  proceed  the  internal  anterior  thoracic  nerve,  the  in- 
ner head  of  the  median,  the  ulnar,  the  internal  cutaneous,  and 
the  lesser  internal  cutaneous  ;  from  the  posterior  cord  proceed 
the  three  subscapular  nerves,  the  circumflex,  and  the  musculo- 
spiral. 

The  anterior  thoracic  nerves  have  been  described  (p.  312). 

Subscapular  Nerves.  —  The  three  subscapular  nerves  are 
found  on  the  surface  of  the  subscapularis.  They  come  from 
the  posterior  cord  of  the  brachial  plexus,  and  supply,  respec- 
tively, the  latissimus  dorsi,  teres  major,  and  subscapularis. 
The  nerve  to  the  latissimus  dorsi  {long  subscapular  nen^e')  runs 
with  the  anterior  branch  of  the  subscapular  artery  to  the  lower 
border  and  inner  surface  of  the  muscle. 

The  neri'e  to  the  teres  major  is  either  a  branch  of  the  preced- 
ing, or  comes  separately  from  the  posterior  cord.  It  lies  nearer 
to  the  humerus  than  the  long  subscapular.  It  gives  off  also  a 
small  branch  to  the  anterior  border  of  the  subscapularis. 

The  nerve  to  the  subscapularis  arises  from  the  posterior  cord, 
higher  than  the  others,  and  enters  the  muscle  not  far  from  its 
upper  border  in  company  with  a  small  artery. 

Circumflex  Nerve.  ^ — The  circumflex  nerve  accompanies  the 
posterior  circumflex  artery.  This  large  nerve  comes  from  the 
posterior  cord,  and,  after  giving  a  small  filament  to  the  shoulder- 
joint,  passes,  with  its  companion  artery,  through  the  quadrilate- 


LATISSIMUS    DORSI.  323 

ral  space  (Fig.  123  p.  319)  to  the  under  surface  of  the  deltoid. 
Here  the  nerve  divides  into  an  upper  and  a  lower  branch.  The 
upper  supplies  the  anterior  part  of  the  deltoid  and  the  skin  over 
it ;  the  /^ze/^r  supplies  the  back  part  of  the  deltoid,  and  gives  the 
nerve  to  the  teres  minor,*  upon  which  nerve  sometimes  a  little 
gangliform  swelling  can  be  seen  :  it  enters  the  under  aspect  of 
the  middle  of  this  muscle.  After  furnishing  these  muscular 
branches,  the  nerve  turns  round  the  posterior  border  of  the 
deltoid,  and  diverges  in  filaments  which  supply  the  skin  over 
the  back  of  this  muscle  and  over  the  long  head  of  the  triceps. 

Latissimus  Dorsi.  —  This  broad,  flat  muscle  forms  the  pos- 
terior margin  of  the  axilla.  It  arises  from  the  external  lip  of 
the  crest  of  the  ilium,  from  an  aponeurosis  attached  to  the  spi- 
nous processes  of  the  six  lower  thoracic,  of  all  the  lumbar,  and 
of  the  sacral  vertebrae  and  their  supraspinous  ligament,  and  by 
fleshy  digitations  from  the  three  or  four  lower  ribs,  interdigitat- 
ing  with  those  of  the  external  oblique  ;  in  some  cases,  as  it 
passes  over  the  inferior  angle  of  the  scapula,  it  has  an  additional 
origin  from  the  angle.  Its  fibres  converge  from  this  large  ori- 
gin, and  the  muscle  is  inserted  into  the  bottom  of  the  bicipital 
groove  of  the  humerus  — as  high  up  as  the  lesser  tuberosity  — 
by  a  broad  flat  tendon,  which  curves  round  the  lower  border  of 
the  teres  major.  The  axillary  vessels  and  nerves  lie  upon  the 
tendon  close  to  its  insertion.  Its  neive  is  the  long  subscapular 
branch  from  the  posterior  cord  of  the  brachial  plexus,  and  it 
enters  the  muscle  close  to  its  anterior  border,  in  company  with 
a  large  branch  of  the  subscapular  artery  (Fig.  125). 

Teres  Major.  —  This  muscle  lies  behind,  and  to  the  inner 
side  of  the  latissimus  dorsi,  is  closely  connected  with  it,  and 
assists  in  forming  the  posterior  boundary  of  the  axilla.  It  arises 
from  the  oval  surface  of  the  dorsal  aspect  of  the  lower  angle  of 
the  scapula,  and  from  the  fibrous  septa  between  it  and  the  teres 
minor  and  infraspinatus,  and  is  inserted  by  a  broad  flat  tendon, 
about  two  inches  (5  em.)  in  length,  behind  the  latissimus  dorsi, 
into  the  posterior  margin  of  the  bicipital  groove  of  the  humerus. 
The  tendon  extends  below  that  of  the  latissimus  dorsi,  and  a  bursa 
or  sac,  lubricated  with  serum,  intervenes  between  the  two  tendons. 
The  action  of  this  and  the  preceding  muscle  is  to  draw  the 
humerus  inwards  and  backwards.     The  latissimus  dorsi  when 


*  This  branch  to  the  teres  minor  is  said  to  be  constant  in  all  mammalia  that 
have  been  examined  in  reference  to  this  point. 


324 


MUSCLES    OF    THE    BACK. 


Fu;.  125.— Muscles  of  the  Back  (Superficial). 

Trapezius.  2.  Latissimus  dorsi.  3,  3.  Pacro-lumbar  aponeurosis.  4.  Portion  of  the  fascia 
anterior  to  the  latissimus  dorsi.  5.  Fasciculus  by  which  this  muscle  is  attached  to  the  crest 
of  the  ilium.  6.  External  border  of  the  same.  7.  'J'eres  major.  8.  Superior  border  of  the 
latissimus  dorsi  passing  over  the  teres  major.  9.  Rhomboid  major.  10.  Rhomboid  minor. 
II.  Superior  border  of  the  serratus  post,  superior.  12,  12,  12.  The  three  fasciculi  of  the  ser- 
ratus  pest,  inferior.  13.  Sterno-cleido-mastoid.  14.  Splenius.  15.  Levator  anguli  scapula-. 
16.  Infra-spinatus.  17.  Teres  minor.  18.  Teres  major.  19.  Cut  latissimus  dorsi.  20.  Scapu- 
lar attachment  of  the  latissimus  dorsi.  21.  Inferior  portion  of  the  serratus  magnus.  22,  22. 
Posterior  part  of  the  internal  oblique.  23.  Posterior  aponeurosis  of  this  muscle  uniting  with 
that  of  the  serratus  posticus  inferior  and  the  latissimus  dorsi,  forming  the  sacro-lumbar  aponeu- 
rosis. 24.  (Gluteus  maximus.  25.  Cut  origin  of  this  muscle.  26.  Gluteus  medius.  27. 
Pjrramidalis.  28.  The  tendon  oif  the  obturator  intenius  and  tlie  superior  and  inferior 
gemelli.  29.  Quadratus  femoris.  30.  Sacro-lumbalis  and  longissimus  dorsi.  31.  Deltoid. 
32.  Triceps. 


SERRATUS    MAGNUS.  325 

the  humerus  is  fixed  will  raise  the  trunk,  is  used  in  turning  a 
back  summersault,  and  by  its  costal  attachments  will  assist  in 
forced  inspiration.  Its  ficri'c  is  the  middle  subscapular,  and  lies 
along  the  dorsalis  scapulas  artery  (Figs.  121,  125). 

Subscapularis.  —  This  muscle  arises  from  the  posterior  two- 
thirds  of  the  subscapular  fossa  of  the  scapula,  with  the  excep- 
tion of  the  angles,  neck,  and  the  posterior  border,  and  from  the 
intermuscular  septa  attached  to  the  bony  ridges.  Its  fibres  con- 
verge to  a  strong  tendon,  which  passes  under  the  axillary  vessels 
and  nerves,  over  the  inner  side  of  the  shoulder-joint,  and  is 
inserted  into  the  lesser  tuberosity  of  the  humerus,  and  into  the 
neck  of  the  humerus  for  an  inch  {2.^  cm.)  below  it.  The  tendon 
of  the  muscle  is  intimately  connected  with  the  capsular  ligament 
of  the  shoulder-joint,  and  between  the  base  of  the  coracoid  pro- 
cess and  the  tendon  is  a  bursa,  which  communicates  with  the 
joint.  Its  action  is  to  rotate  the  humerus  inwards,  and  when 
the  arm  is  raised  to  draw  it  to  the  side.  Its  nerves  come  from 
the  upper  and  middle  subscapular  nerves. 

Serratus  Magnus.  This  muscle  covers  the  side  of  the  chest 
like  a  girth.  It  arises  from  the  front  of  the  outer  surfaces  of 
the  eight  upper  ribs  by  nine  slips  or  digitations,  the  second  rib 
having  two.  Its  fibres  converge,  and  are  inserted  into  the  pos- 
terior border  of  the  scapula  in  the  following  manner  :  the  first 
two  digitations  are  attached  into  the  upper  angle  of  the  scapula  ; 
the  third  and  fourth  digitations  along  nearly  the  whole  length 
of  the  posterior  border ;  the  remainder  are  inserted  into  the 
inferior  angle.  Its  action  is  to  draw  the  scapula  forwards,  i.e., 
rotates  the  scapula  on  the  acromial  end  of  the  clavicle.  In 
paralysis  of  the  deltoid  this  rotation  is  very  marked  by  fixing 
the  scapula  on  the  clavicle.  When  the  scapula  is  fixed  the 
muscle  will  elevate  the  ribs,  and  hence  is  an  accessory  inspira- 
tory muscle,  as  can  be  seen  in  the  asthmatic.  After  the  deltoid 
has  raised  the  arm  to  a  right  angle  with  the  trunk  this  muscle 
with  trapezius  will  elevate  the  arm  above  the  head.  (A.  H.)  It 
is  supplied  by  the  following  neroe,  which  is  seen  on  its  outer 
surface. 

Posterior  Thoracic  or  External  Respiratory  Nerve  of 
Bell.  — This  nerve  supplies  the  serratus  magnus  only.  It  comes 
from  the  fifth  and  sixth  cervical  nerves  ;  and,  after  passing 
through  the  scalenus  medius,  runs  behind  the  axillary  vessels, 
along  the  outer  surface  of  the  serratus  magnus,  each  digitation 
receiving  a  separate  filament. 


326 


DISSECTION    OF    THE    UPPER    ARM. 


DISSECTION    OF    THE    UPPER    ARM. 


Surface  Marking.  —  In  front  of  the  upper  arm  may  be  dis- 
tinguished the  long  prominence  of  the  biceps  muscle,  and  lower 
down  at  the  bend  of  the  elbow  its  tendon 
may  be  easily  felt.  The  bend  of  the  elbow, 
in  muscular  subjects,  presents  a  triangular 
depression,  with  its  boundaries  formed  on  the 
inner  side  by  the  pronator  teres,  and  on  the 
outer  side  by  the  brachio-radialis  {supinator 
lojigiis).  Superficially  in  this  space  the  sub- 
cutaneous veins  can  be  recognized,  of  which 
a  fuller  description  will  be  entered  into  later 
on.  On  the  inner  side  of  the  elbow,  the  in- 
ternal condyle  of  the  humerus  is  very  prom- 
inent, and  behind  this  is  the  olecranon  ;  be- 
tween these  is  a  hollow  in  which  may  be  felt 
the  ulnar  nerve.  The  olecranon  is  situated 
nearer  the  internal  than  the  external  condyle, 
which  is  visible  on  the  outer  side;  below  this, 
is  a  dimple  which  corresponds  with  the  head 
of  the  radius. 

Dissection.  —  Continue  the  incision  down 
the  inner  side  of  the  arm  as  far  as  two  inches 
(5  cm)  below  the  elbow,  and  then  make  a 
transverse  incision  from  the  inner  to  the  outer 
side  of  the  forearm.  Reflect  the  skin,  and 
trace  out  the  cutaneous  nerves  and  the  nume- 
rous veins  in  front  of  the  elbow. 

Cutaneous  Nerves.  —  On  the  inner  side 
of  the  arm  are  the  intercosto-humeral,  the 
internal  cutaneous  branch  of  the  musculo- 
spiral,  the  internal  cutaneous,  and  the  lesser 
internal  cutaneous  (nerve  of  Wrisberg)  nerves ; 
on  the  outer  side  are  the  cutaneous  branches 
of  the  circumflex,  the  external  cutaneous 
branches  of  the  musculo-spiral,  and  lower 
down  is  the  musculo-cutaneous  nerve. 


Fig.  126.  —  Distribu- 
tion OF  Cutaneous 
Nerves TOTHE  Fkont 
OF  THE  Shoulder  and 
Arm. 

I.  Acromial  brandies  of 
the  superficial  cervical 
plexus.  2.  clavicular 
branches  of  the  super- 
fidal    cervical    plexus. 

3.  Cutaneous  branches 
of  the  circumflex  nerve. 

4.  Branches  of  the  in- 
ternal cutaneous  nerve. 

5.  External  cutaneous 
branch  of  the  musculo- 
spiral  nerve.  6.  Inter- 
nal cutaneous  nerve. 
7.  Its  posterior  cutane- 
ous branch.  8.  'I'he 
cutaneous  branch  of 
the  musculo-cutaneous 
nerve. 


The  filament.s  of  the  i7itercosto-Jmnieral  7terves  (p.  314) 
descend  along  the  inner  and  posterior  part  of  the  arm  as 
far  as  the  olecranon,  and  communicate  with  the  internal  cutaneous  branch  of  (he 
musculo  spiral  nerve. 


CUTANEOUS    NERVES    OF    THE    ARM. 


327 


The  internal  cutaneous  nerve  perforates  the  fascia,  with  the  basilic  vein,  about 
the  middle  of  the  arm,  and  divides  into  an  anterior  and  a  posterior  branch;  the 
anterior  passes  down  in  front  of  the  arm  (as  a  rule,  beneath  the  median  basilic 
vein),  and  supplies  the  skin  as  far  as  the  wrist,  communicating  with  a  cutaneous 
branch  of  the  ulnar  nerve ;  the  posterior  winds  round  to  the  back  of  the  forearm 
behind  the  internal  condyle  as  far  as  the  wrist,  and  communicates  above  the  elbow 
with  the  nerve  of  Wrisberg,  and  above  the  wrist  with  the  dorsal  branch  of  the 
ulnar  nerve. 

The  lesser  internal  cutaneous  {nerve  of  Wrisberg)  perforates  the  fascia  about 
the  lower  third  of  the  arm,  and  supplies  the  skin  over  the  internal  condyle  and 
the  olecranon.  This  nerve,  as  it  lies  close  to  the  axillary  vein,  communicates 
with  the  tirst  or  second  intercosto-humeral  nerve. 


Basilic  vein. 


Median  basilic  vein. 


Deep  median  vein. 


Cephalic  vein. 


Median  cephalic  vein. 


Median  vein. 


Fig.  127.  —  Superficial  Veins  and  Nerves  at  the  Bend  of  the  Left  Elbow. 


The  internal  ciitaneoics  branch  of  the  musculo-spiral  ne>"ve  pierces  the  fascia 
and  supplies  the  skin  of  the  inner  and  posterior  aspect  of  the  middle  of  the  arm 
as  far  as  the  olecranon. 

The  cittaneoiis  branches  of  the  circumflex  nerve  pierce  the  fascia  over  the  inser- 
tion of  the  deltoid,  and  supply  the  skin  of  the  upper  half  of  the  arm  on  its 
outer  side. 

The  external  cutaneotis  branches  of  the  musculo-spiral  nerve  are  two  in  number: 
the  upper  and  smaller  accompanies  the  cephalic  vein  in  the  lower  half  of  the  arm; 
the  lower  may  be  traced  down  the  outer  and  back  part  of  the  forearm  nearly  as 
far  as  the  wrist,  where  it  joins  the  posterior  branch  of  the  musculocutaneous 
nerve. 

On  the  outer  side  of  the  tendon  of  the  biceps  the  cutaneous  branch  of  the 
musculo-cutaneous  nerve  perforates  the  fascia,  and  divides  into  many  filaments, 
which  supply  the  skin  of  the  outer  part  of  the  forearm. 


328  MEDIAN    BASILIC    VEIN. 

Disposition  of  Veins  in  Front  of  the  Elbow. — Atten- 
tion should  now  be  directed  to  the  disposition  of  the  veins  in 
front  of  the  elbow.  In  cleaning  these  veins,  take  care  not  to 
divide  the  branches  of  the  internal  and  external  cutaneous 
nerves  which  pass  over  and  under  them. 

The  following  is  the  ordinary  arrangement  of  the  superficial 
veins  at  the  bend  of  the  elbow  (Fig.  127).  On  the  outer  side 
is  the  radial ;  on  the  inner  side  is  the  iibiar  vein,  formed  by 
the  junction  of  the  anterior  and  posterior  ulnar  cutaneous  veins  ; 
in  the  centre  is  the  median,  which  divides  into  two  branches, 
the  external  of  which,  uniting  with  the  radial  to  form  the 
cephalic  vein,  is  called  the  vicdian  cephalic  ;  the  internal,  uniting 
with  the  ulnar  to  form  the  basilic,  is  named  the  median  basilic. 
Near  its  bifurcation,  the  median  vein  communicates  by  a  branch 
(mediana  profunda)  with  the  deep  veins  which  accompany  the 
arteries  of  the  forearm. 

Trace  the  cephalic  veiji  up  the  arm.  It  runs  along  the  outer 
border  of  the  biceps  to  the  groove  between  the  pectoralis  major 
and  the  deltoid,  and  dipping  down  between  these  two  muscles, 
terminates  in  the  axillary  vein  immediately  above  the  pectoralis 
minor. 

The  basilic  vein,  the  largest  of  the  veins  of  the  upper  arm, 
ascends  along  the  inner  side  of  the  arm  with  the  internal  cuta- 
neous nerve.  Near  the  middle  of  the  arm,  it  perforates  the 
fascia,  and  empties  itself  either  into  the  internal  vena  comes  of 
the  brachial  artery  or  into  the  axillary  vein. 

Relation  of  the  Cutaneous  Nerves  and  Veins  at  the 
Elbow. — The  principal  branches  of  the  cutaneous  nerres  pass 
beneath  the  veins ;  that  is  to  say,  as  a  rule,  the  internal  cuta- 
neous passes  behind  the  median  basilic  vein,  and  the  external 
cutaneous  behind  the  median  cephalic  :  but  it  should  be  remem- 
bered that  many  small  filaments  cross  in  front  which  are  exposed 
to  injury  in  venesection  (Fig.  127). 

Relation  of  Median  Basilic  Vein  to  Brachial  Artery. — 
Since  the  median  basilic  vein  is  larger  than  the  median  cephalic, 
and,  on  account  of  the  strong  fascia  beneath,  more  easily  com- 
pressible, it  is  usually  chosen  for  venesection ;  its  position, 
therefore,  in  reference  to  the  brachial  artery,  becomes  important. 
The  vein  is  only  separated  from  the  artery  by  the  setnilnnar 
fascia,  derived  from  the  tendon  of  the  biceps.  This  fascia  is 
in  some  subjects  remarkably  thin.  Sometimes  the  artery  lies 
above  the  fascia,  in  contact  with  the  vein.     In  choosing,  there- 


MUSCULAR    FASCIA.  329 

fore,  this  vein  for  venesection,  there  is  a  risk  of  wounding  the 
artery  ;  hence  the  practical  rule,  to  bleed  either  from  the  median 
cephalic,  or  from  the  median  basilic  above  the  situation  where 
it  crosses  the  brachial  artery. 

Lymphatic  Glands.  —  Immediately  above  the  internal  con- 
dyle, in  the  neighborhood  of  the  basilic  vein,  wc  find  one  or 
two  small  lymphatic  glands.  Others  may  be  found  higher  up 
along  the  inner  side  of  the  arm.  A  gland  is  occasionally  met 
with  at  the  bend  of  the  elbow  ;  but  never  below  this  joint. 
These  little  glands  are  the  first  which  are  liable  to  become 
tender  and  enlarged  after  a  poisoned  wound  of  the  hand. 

Muscular  Fascia  and  its  Connections.  — The  fascia  which 
invests  the  muscles  of  the  upper  arm  is  a  continuation  of  the 
fascia  of  the  trunk  and  the  axilla.  This  membrane  varies  in 
density  :  thus  it  is  thin  over  the  biceps,  stronger  on  the  inner 
side  of  the  arm,  to  protect  the  brachial  vessels  and  nerves,  and 
strongest  over  the  triceps.  At  the  upper  part  of  the  arm  it  is 
connected  with  the  coracoid  process  and  the  clavicle ;  it  is 
strengthened  at  the  axilla  by  an  expansion  from  the  tendons  of 
the  pectoralis  major  and  latissimus  dorsi ;  posteriorly,  it  is  at- 
tached to  the  spine  of  the  scapula.  The  fascia  surrounds  the 
brachial  vessels  with  a  sheath,  and  furnishes  partitions  which 
separate  the  muscles  from  each  other.  Of  these  partitions,  the 
most  marked  are,  the  external  and  internal  intennuscnlar  septa, 
which  divide  the  muscles  on  the  anterior  from  those  on  the 
posterior  surface  of  the  upper  arm.  These  septa  are  attached 
to  the  condylar  ridges  of  the  humerus  and  to  the  condyles. 
The  internal  interninscnlar  septnm,  the  stronger  of  the  two, 
begins  at  the  insertion  of  the  teres  major,  and  is  connected 
with  the  tendinous  insertion  of  the  coraco-brachialis ;  it  sep- 
arates the  triceps  extensor  from  the  brachial  anticus,  to  both  of 
which  it  affords  attachment  to  their  muscular  fibres.  It  is 
pierced  by  the  ulnar  nerve  and  the  inferior  profunda  and  anas- 
tomotic arteries.  The  external  intermuscular  septum  commences 
from  the  insertion  of  the  deltoid,  and  separates  the  brachialis 
anticus,  the  supinator  longus,  and  the  extensor  carpi  radialis 
longior  in  front,  from  the  triceps  extensor  behind,  to  all  of  which 
muscles  it  affords  attachment.  It  is  pierced  by  the  musculo- 
spiral  nerve  and  the  superior  profunda  artery. 

At  the  lower  part  of  the  upper  arm  the  fascia  is  remarkably 
strong,  especially  where  it  covers  the  brachialis  anticus  and  the 
brachial  vessels,  and  is  continued  over  the  muscles  on  the  inner 


330  THE    BICEPS. 

side  of  the  forearm.  At  the  back  of  the  elbow  the  fascia  is 
attached  to  the  tendon  of  the  triceps  and  the  olecranon. 

Dissection.  —  Now  remove  the  fascia  corresponding  to  the 
incisions  through  the  skin,  in  order  to  see  the  muscles  on  the 
front  of  the  arm  —  namely,  the  biceps,  the  coraco-brachialis, 
and  the  brachialis  anticus.  The  long,  rounded  muscle  in  front 
is  the  biceps ;  the  muscle  attached  with  it  to  the  coracoid 
process  is  the  coraco-brachialis ;  and  the  broad  flat  muscle 
covering  the  lower  end  of  the  humerus  is  the  brachialis  anticus. 

Biceps.  — The  biceps,  as  its  name  implies,  arises  by  two 
heads  —  a  long  and  a  short.  The  sJiort  Jicad  arises  from  the 
tip  of  the  coracoid  process  of  the  scapula,  by  a  thick,  flat 
tendon  in  common  with  a  slender  muscle  on  its  inner  side, 
called  the  coraco-brachialis.  The  lono;  head  arises  from  the 
upper  border  of  the  glenoid  fossa  of  the  scapula  and  the  glenoid 
ligament,  by  a  long,  rounded  tendon,  which,  traversing  the 
shoulder-joint,  passes  over  the  head  of  the  humerus ;  there 
pierces  the  capsular  ligament,  and  descends  in  the  groove  be- 
tween the  two  tuberosities.  The  tendon  is  retained  in  the 
groove  by  a  fibrous  bridge  derived  from  the  capsule  of  the  joint, 
and  connected  with  the  tendon  of  the  pectoralis  major.  Divide 
this  bridge,  and  see  that  the  synovial  membrane  of  the  joint  is 
reflected  round  the  tendon  and  accompanies  it  for  about  two 
inches  (5  cm.)  down  the  groove,  thus  forming  a  synovial  fold. 
The  object  of  this  is  to  facilitate  the  play  of  the  tendon  and  to 
carry  little  arteries  (from  the  anterior  circumflex)  for  its  supply. 
The  two  heads  unite  about  the  middle  of  the  arm  and  form  a 
single  muscle,  which  terminates  on  a  strong  flat  tendon  of  con- 
siderable length  ;  this  dips  down  into  the  triangular  space  at 
the  bend  of  the  elbow,  and,  after  a  slight  twist  upon  itself,  is 
inserted  into  the  posterior  part  of  the  tubercle  of  the  radius. 
The  anterior  part  of  the  tubercle,  over  which  the  tendon  plays, 
is  crusted  with  cartilage,  and  a  bursa  intervenes  to  diminish 
friction.  The  most  internal  fibres  of  the  muscle  are  inserted 
into  a  strong,  broad  aponeurosis,  which  is  prolonged  from  the 
inner  border  of  the  tendon  to  the  fascia  on  the  inner  side  of 
the  forearm.  This  aponeurosis,  called  the  semilunar  fascia  of 
the  biceps,  protects  the  brachial  vessels  and  the  median  nerve  at 
the  bend  of  the  elbow  (Fig.  128). 

The  action  of  the  biceps  is  twofold,  i.  It  is  a  flexor  of  the 
forearm.  2.  It  is  a  powerful  supinator  of  the  forearm  in  con- 
sequence of  its  insertion  into  the  posterior  part  of  the  tubercle 


CORACO-BRACIIIALIS. 


331 


of  the  radius.     Its  power  of  supination  is  greatest  when  the 

forearm  is    half  bent,   because  its  tendon  is  then  inserted  at 

a  right  angle.     Why  does  the 

long  tendon   pass  through  the 

shoulder-joint  ?      It  acts  like  a 

strap,  and  confines  the  head  of 

the  humerus  in  its  proper  centre 

of  motion.*    But  for  this  tendon 

the  head  of  the  bone,  when  the 

deltoid    acts,    would    be    pulled 

directly     upwards     and     strike 

against  the  under  surface  of  the 

acromion.     When  the  tendon  is 

ruptured,  or  dislocated  from  its 

groove,  a  man  can  move  his  arm 

backwards  and  forwards,  but  he 

cannot  raise  the  smallest  weight. 

The  biceps  is  supplied  with  blood 

by  a  branch  from  the  brachial, 

which  runs  into   the  middle  of 

its  inner  side,  and  divides  into 

ascending     and     descending 

branches.     Its  nerve  comes  from 

the  musculo-cutaneous. 

Coraco-Brachialis.  —  This 
thin  muscle  is  situated  at  the 
upper  part  of  the  arm,  and  runs 
parallel  to  the  inner  border  of 
the  short  head  of  the  biceps. 
It  arises  by  fleshy  fibres  from 
the  point  of  the  coracoid  pro- 
cess, in  common  with  the  short 
head  of  the  biceps,  and  from  a 
fibrous  septum  which  lies  be- 
tween them.  The  muscle  de- 
scends backwards  and  outwards, 
and  terminates  on  a  flat  tendon, 
which  is  inserted  into  the  inner 


E.SALLE  s. 
Fig.  128.  —  Anterior  Muscles  of  the  Arm. 

I.  Biceps.  2.  Short  head  of  the  biceps.  3. 
Long  head  of  the  same.  4.  Tendon  attached 
to  the  tuberosity  of  the  radius.  5.  Semilunar 
fascial  aponeurosis  of  the  biceps.  6.  Coraco- 
brachialis.  7,  8.  The  two  portions  of  the  pec- 
toralis  major  forming  a  groove  with  its  con- 
cavity above.  9.  Attachment  of  the  latissimus 
dorsi.  10.  Teres  major.  11.  Subscapularis. 
12.  Brachialis  anticus.  13.  Long  head  of  the 
triceps.  14.  Internal  head  of  the  triceps. 
15.  Supinator  longus  or  brachio-radialis.  16. 
Extensor  carpi  radialis  longior. 


*  Another  action  of  the  long  tendon  of  the  biceps  would  seem  to  be  that  of 
an  internal  rotator  of  the  humerus  when  that  bone  is  rotated  externally.  The 
marked  prominence  of  the  internal  tuberosity  and  the  groove  on  its  outer  aspect 
would  favor  this  view. 


332  BRACHIAL    ARTERY. 

side  of  the  middle  of  the  humerus,  between  the  brachialis  an- 
ticus  and  the  inner  head  of  the  triceps.      Its  action  is  to  draw 
the  humerus  forwards  and  inwards  —  e.g.,  in  bringing  the  gun  . 
up  to  the  shoulder.     It  is  supplied  by  a  branch  from  the  mus- 
culo-cutaneous  nerve  w^hich  pierces  it  (Fig.  128). 

Concerning  the  coraco-brachiahs,  remember:  i.  That  the 
musculo-cutaneous  nerve  runs  through  it ;  2.  That  its  inner 
fieshy  border  is  the  guide  to  the  axillary  artery  in  the  last  part 
of  its  course  ;  3.  That  the  brachial  artery  lies  upon  its  flat 
tendon  of  insertion,  and  can  here  be  effectually  compressed  by 
the  finger  or  the  tourniquet. 

The  coraco-brachialis  and  biceps  are  covered  at  their  upper 
part  by  the  deltoid  and  pectoralis  major.  The  head  of  the 
humerus  rolls  beneath  the  coraco-brachialis  and  short  origin  of 
the  biceps  ;  and  a  large  b^irsa  is  interposed  between  these  mus- 
cles and  the  tendon  of  the  subscapularis,  which  covers  the  head 
of  the  bone. 

Brachialis  Anticus.  —  This  broad  muscle  covers  the  lower 
half  of  the  humerus,  and  is  partially  concealed  by  the  biceps. 
Between  the  two  muscles  is  the  musculo-cutaneous  nerve,  which 
supplies  them  both. 

It  arises  from  the  humerus  by  a  fleshy  digitation  on  either 
side  of  the  tendon  of  the  deltoid  ;  from  the  lower  half  of  the 
front  and  inner  surfaces  of  the  bone,  and  from  the  intermuscular 
septa.  The  muscle,  becoming  thicker  and  broader,  covers  the 
front  of  the  capsule  of  the  elbow-joint,  to  which  it  is  more  or 
less  attached,  and  terminates  on  a  tendon,  which  is  inserted  in  a 
pointed  manner  into  the  anterior  surface  of  the  coronoid  process 
of  the  ulna.  Its  action  is  to  bend  the  forearm.  Its  nerves 
come  from  the  musculo-cutaneous,  and  it  usually  receives  in 
addition  a  small  branch  from  the  musculo-spiral  (Fig.  1 2 1 ,  p.  3 1 8). 

Now  examine  the  course  and  relations  of  the  brachial  vessels 
and  nerves. 

Course  and  Relations  of  the  Brachial  Artery. — The 
brachial  artery  —  the  continuation  of  the  axillary  —  takes  its 
name  at  the  lower  border  of  the  teres  major.  It  runs  down  the 
anterior  and  the  inner  side  of  the  arm,  along  the  inner  border 
of  the  coraco-brachialis  and  biceps,  to  about  an  inch  (2.5  cm) 
below  the  elbow,  where  it  divides,  near  the  coronoid  process  of 
the  ulna,  into  the  radial  and  ulnar  arteries. 

Thus  its  direction  corresponds  with  a  line  drawn  from  the 
deepest  part  of  the  axilla  to  the  middle  point  between  the  con- 
dyles of  the  humerus. 


BRACHIAL    ARTERY.  333 

In  the  upper  part  of  its  course  it  lies  on  the  long  and  inner 
heads  of  the  triceps  (from  the  long  head  it  is  separated  by 
the  musculo-spiral  nerve  and  superior  profunda  artery^  ;  in  the 
middle,  it  lies  on  the  tendon  of  the  coraco-brachialis ;  in  the 
lower  part,  on  the  brachialis  anticus. 

In  front  of  the  artery  are  the  internal  cutaneous  nerve,  the 
median  basilic  and  basilic  veins  ;  the  median  nerve,  which  crosses 
obliquely  over  the  artery,  being  on  its  outer  side  near  the  axilla, 
and  on  its  inner  side  near  the  elbow  ;  and  lastly,  the  artery  is 
more  or  less  overlapped,  in  the  first  part  of  its  course,  by  the 
coraco-brachialis,  lower  down  by  the  fleshy  belly  of  the  biceps  ; 
the  inner  borders  of  these  muscles,  in  their  respective  situations, 
being  the  best  guides  to  the  artery. 

On  the  outer  side  of  the  artery  are,  the  median  nerve,  the 
coraco-brachialis,  and  biceps. 

On  the  inner  side  are,  at  first,  the  ulnar  nerve,  the  internal 
cutaneous  nerves  ;   and,  below,  the  median  nerve. 

The  artery  is  accompanied  by  two  veins  {vencB  comites)  and 
the  median  nerve,  all  of  which  are  invested  in  a  common 
sheath  of  fascia. 

The  ulnar  nerve  runs  along  the  inner  side  of  the  artery  as 
far  as  the  middle  of  the  arm.  Below  this  point,  the  nerve 
leaves  the  artery,  and  passes  through  the  internal  intermuscular 
septum  to  get  behind  the  internal  condyle. 

About  the  middle  of  the  humerus,  the  artery  lies  for  nearly 
two  inches  (5  cm.)  on  the  tendon  of  the  coraco-brachialis,  and 
is  so  close  to  the  bone  that  it  can  be  effectually  compressed, 
provided  the  pressure  be  made  in  the  proper  direction  —  namely, 
outwards.      Here,  too,  it  is  crossed  by  the  median  nerve. 

At  the  bend  of  the  elbow  the  artery  is  crossed  by  the  semi- 
lunar fascia  from  the  biceps.  It  enters  a  triangular  space,* 
bounded  by  the  pronator  radii  teres  internally,  and  by  the 
brachio-radialis  externally.  It  sinks  into  this  space,  with  the 
tendon  of  the  biceps  to  its  outer  side,  and  the  median  nerve  to 
its  inner ;  all  three  rest  upon  the  brachialis  anticus.  To  com- 
press the  artery  here,  pressure  should  be  made  directly  back- 
wards. Opposite  the  coronoid  process  of  the  ulna  it  divides 
into  the  radial  and  ulnar  arteries. 

Two  veins,  of  which  the  internal  is  the  larger,  lie  in  close 
contact  with  the  brachial  artery,  and  communicate  at  frequent 
intervals  by  transverse  branches.  Near  the  axilla  they  jcin  and 
form  the  axillary  vein. 

*  Anticiipital  space. 


jj4 


BRANCHES  OF  BRACHIAL  ARTERY. 


Branches  of  Brachial  Artery. — The  brachial  artery  gives 
off  four  branches,  all  from  its  inner  side :  namely,  the  superior 
profunda,  the  inferior  profunda,  the  nutrient  artery,  and  the 
anastomotica  magna.  It  also  distributes  muscular  branches  to 
the  coraco-brachialis  and  biceps,  which  are  given  off  from  its 
outer  side. 

a.  The  proftoida  superior  arises  from  the  inner  and  back  part  of  the  brachial 
artery,  immediately  below  the  tendon  of  the  teres  major.*     It  -winds  round  the 


Superior  profunda. 


nterosseous  recurrent. 


Radial  recurrent. 


Posterior  interosseous. 


Inferior  profunda. 

Anastomotica  magna. 

Anterior  ulnar  recurrent. 
Posterior  ulnar  recurrent. 

Common  interosseous. 
Anterior  interosseous. 


Fig.  129.  —  Plan  of  the  Chief   Branches  of  the  Brachial  Artery   and  the  Arterial 
Inosculations  about  the  Right  Elbow- Joint. 

back  of  the  humerus,  between  the  outer  and  inner  heads  of  the  triceps,  accom- 
panied by  the  musculo-spiral  nerve,  and,  a  little  above  the  middle  of  the  arm, 
divides  into  two  branches,  which  run  for  some  distance  on  either  side  of  the  nerve. 
One  of  these  runs  in  the  substance  of  the  triceps  muscle,  with  the  nei-ve  to  the 
anconeous,  as  far  as  the  olecranon,  and  anastomoses  with  the    posterior  ulnar 

*  If  the  profunda  be  not  in  its  usual  place,  look  for  it  above  the  tendon  of  the 
latissimus  dorsi,  where  it  will  probably  be  given  off  from  a  common  trunk  with 
the  posterior  circumflex. 


MEDIAN    NERVE.  335 

recurrent,  the  interosseous  recurrent,  and  anastomotica  magna  arteries :  the  other 
branch  accompanies  the  musculo-spiral  nerve  to  tiie  outer  side  of  the  arm,  where 
it  perforates  the  external  intermuscular  septum.  It  then  descends  deep  in  the 
interval  between  the  brachialis  amicus  and  supinator  radii  longus,  and  terminates 
in  numerous  ramifications,  some  of  which  pass  in  front  of  the  external  condyle, 
others  behind  it,  to  inosculate  with  the  radial  and  interosseous  recurrent  arteries. 

Before  its  division,  the  superior  profunda  sends  several  branches  to  the  deltoid, 
coraco-brachialis,  and  the  triceps,  some  of  which  inosculate  with  the  circumflex. 
These  assist  in  establishing  a  collateral  circulation  when  the  brachial  arteiy  is 
ligatured  above  the  origin  of  the  profunda. 

b.  The  profunda  vi/erior  arises  from  the  brachial,  opposite  to  the  insertion  of 
the  coraco-brachialis,  or  sometimes  by  a  common  trunk  with  the  superior  profunda. 
It  runs  with  the  ulnar  nerve  on  the  inner  head  of  the  triceps  (which  it  supplies), 
passes  through  the  internal  intermuscular  septum,  and  then  descends  to  the  in- 
terval between  the  internal  contlyle  and  the  olecranon,  inosculating  with  the 
posterior  ulnar  recurrent  and  anastomotica  magna  arteries.  It  also  sends  a  small 
branch  down  in  front  of  the  internal  condyle  to  anastomose  with  the  anterior 
ulnar  recurrent. 

c.  The  nutrient  artery  of  the  humerus  arises  sometimes  from  the  brachial, 
sometimes  from  the  inferior  profunda.  It  pierces  the  tendon  of  the  coraco- 
brachialis,  runs  obliquely  downwards  through  the  bone,  and  in  the  medullary 
canal  divides  into  ascending  and  descending  branches,  which  anastomose  with  the 
nutrient  vessels  of  the  bone  derived  from  the  periosteum. 

d.  The  anastomotica  mai^na  arises  from  the  inner  side  of  the  brachial,  about 
two  inches  (j"  cm.)  above  the  elbow,  runs  tortuously  inwards,  transversely  across 
the  brachialis  anticus,  and  divides  into  branches,  some  of  which  pass  in  front  of 
the  internal  condyle,  anastomosing  with  the  anterior  ulnar  recurrent  artery;  another 
passes  behind  the  internal  condyle  by  piercing  the  internal  intermuscular  septum, 
and  anastomoses  with  the  inferior  profunda  and  posterior  ulnar  recurrent  arteries; 
and  one  branch  forms  an  arch,  above  the  olecranon  fossa,  with  the  superior 
profunda. 

e.  Numerous  tnusciilar  branches  arise  from  the  outer  side  of  the  brachial  artery; 
one  of  these,  the  bicipital,  more  constant  than  the  rest,  supplies  the  biceps; 
another  runs  transversely  beneath  the  coraco-brachialis  and  biceps,  over  the  inser- 
tion of  the  deltoid,  supplying  this  muscle  and  the  brachialis  anticus. 

Venae  Comites.  —  The  two  veins  which  accompany  the 
brachial  artery  are  continuations  of  the  deep  radial  and  ulnar 
veins.  The  internal  is  usually  the  larger,  and  generally  receives 
the  veins  corresponding  to  the  principal  branches  of  the  artery. 
In  their  course  they  are  connected  at  intervals  by  transverse 
branches  either  in  front  of,  or  behind,  the  artery.  Near  the 
subscapularis,  the  vejta  comes  externa  crosses  obliquely  in  front 
of  the  axillary  artery  to  join  the  vena  comes  interna,  which 
then  takes  the  name  of  axillary. 

Now  trace  the  great  nerves  of  the  upper  arm,  which  proceed 
from  the  brachial  plexus  near  the  tendon  of  the  subscapularis : 
namely,  the  median,  the  musculo-cutaneous,  the  ulnar,  and  the 
musculo-spiral  nerves. 

Median  Nerve.  —  The  viedian  nei"i>c,  so  called  from  the 
course  it  takes  along  the  front  of  the  arm  and  the  forearm, 
arises    by  two  roots,  which  converge   in   front  of  the   axillary 


336  MUSCULO-CUTANEOUS    NERVE. 

artery  (p.  322).  The  external  root  is  derived  from  the  outer 
cord,  in  common  with  the  musculo-cutaneous ;  the  internal 
from  the  inner  cord,  in  common  with  the  ulnar  and  internal  cu- 
taneous. In  its  course  down  the  arm,  the  nerve  is  situated  at 
first  on  the  outer  side  of  the  brachial  artery,  between  it  and  the 
coraco-brachialis  ;  about  the  middle  of  the  arm  the  nerve  crosses 
obliquely  over  (in  some  cases  under)  the  vessel,  so  that  at  the 
bend  of  the  elbow  it  is  found  on  the  inner  side  of  the  artery, 
lying  upon  the  brachialis  anticus,  and  covered  by  the  semilunar 
fascia  from  the  biceps.* 

As  a  summary  of  the  distribution  of  the  median  nerve,  we 
may  say  that  it  supplies  the  two  pronators  and  all  the  flexors  of 
the  forearm  {except  the  flexor  carpi  ulnaris  and  the  ulnar  half 
of  the  flexor  profundus  digitorum)  ;  the  muscles  of  the  ball  of 
the  thumb,  the  two  radial  lumbricales,  both  sides  of  the  thumb, 
fore  and  middle  fingers,  and  the  radial  side  of  the  ring  finger, 
on  their  palmar  aspect  (Fig.  i3o).f 

Musculo-cutaneous  Nerve.— This  nerve  (often  called  the 
external  cutaneous  or  perforans  Casserii)  arises  in  common  with 
the  external  root  of  the  median  from  the  external  cord  of  the 
brachial  plexus  behind  the  pectoralis  minor,  and  is  situated  on 
the  outer  side  of  the  axillary  artery.  It  perforates  the  coraco- 
brachialis  obliquely,  and  then  runs  down  between  the  biceps 
and  the  brachialis  anticus  to  the  outer  side  of  the  arm.  A  little 
above  the  elbow-joint,  between  the  tendon  of  the  biceps  and 
the  supinator  radii  longus,  the  nerve  pierces  the  deep  fascia  and 
becomes  subcutaneous ;  then,  passing  under  the  median  ce- 
phalic vein,  it  divides  into  an  anterior  and  a  posterior  branch,  for 
the  supply  of  the  integuments  of  the  forearm  (Figs.  130,  131). 

The  musculo-cutaneous  nerve,  in  the  upper  part  of  its  course, 
sends  branches  to  the  coraco-brachialis  and  the  short  head  of 

*  I  have  observed  the  following  varieties  relating  to  the  median  nerve,  and  its 
course  in  regard  to  the  artery :  — 

a.  The  roots  may  be  increased  in  number  by  one  on  either  side  of  the  artery; 
or  the  internal  root  may  be  deficient. 

b.  They  may  vary  in  their  position  with  regard  to  the  artery;  botJi  maybe 
situated  behind  the  vessel ;  or  one  Ijehind,  and  the  other  in  front  of  it. 

c.  The  nerve,  formed  in  the  usual  manner,  may  be  joined  lower  down  by  a 
large  branch  from  the  external  cutaneous;  such  a  case  presents  a  junction  of  two 
large  nerves  in  front  of  the  brachial  artei7,  in  the  middle  of  the  arm. 

d.  The  nerve  in  many  cases  crosses  under,  instead  of  over,  the  artery. 

e.  The  nerve  sometimes  runs  parallel  and  external  to  the  artery  ;  or  it  may  run 
parallel  to,  and  in  front  of,  the  artery. 

t  It  sends  two  filaments  to  the  elbow-joint,  which  do  not  supply  any  structure 
in  the  arm.  —  A.  II. 


MEDIAN    AND    ULNAR    NERVES. 


Zl>7 


Fig.  130.  —  Brachial  Portion  of  Musculo- 
cutaneous Median  and  Ulnar  Nerves. 

I.  Musculo-cutaneous.  2.  Branch  of  the  same 
to  the  coraco-brachiahs  muscle.  3.  Branch 
which  supplies  the  biceps.  4.  Branch  to 
brachialis  anticus  muscle.  5.  Anastomosing 
branch  wkich  it  receives  from  the  median.  6. 
Branch  of  the  nerve  at  the  point  where  it 
pierce-  the  aponeurosis  of  the  arm.  7.  Radial 
nerve  as  it  passes  between  the  brachial  anticus 
and  supinator  longus,  or  brachio-radialis.  8. 
External  cutaneous  branch  from  the  radial. 
g.  Divided  trunk  of  the  internal  cutaneous. 
10.  Anterior  or  ulnar  branch  of  the  internal 
cutaneous.  11.  Brachial  portions  of  the  me- 
dian and  ulnar  nerves. 


Fig .  131,  coniiiineti. 
third.     36.  Branches  to  the  adductor  pollicis  and 
the  muscles  of  the  first  and  second  interosseous 
spaces.     37,  38,  39,  40.  Branches  of  radial. 


Fig.  131.  —  Terminal  Portion  of  the  Median 
and  Ulnar  Nerves. 

12.  Forearm,  palmar,  and  digital  portions  of  these 
nerves.  13.  Branch  to  the  pronator  radii  teres 
muscle.  14.  Anterior  muscular  branches  di- 
vided and  removed.  15.  Branch  to  the  flexor 
profundus  digitorum.  16.  Branch  to  the  flexor 
longus  pollicis.  17.  Branch  to  the  interosseous 
membrane.  18.  Palmar  (cutaneous)  branch  di- 
vided below  its  origin,  ig.  To  the  thenar  emi- 
nence. 20.  External  lateral  branch  of  the 
thumb.     21.  Internal  lateral  branch  of  the  same. 

22.  External  digital    branch   to  the  index  finger. 

23.  Common  trunk  to  the  index  and  middle 
fingers.  24.  Digital  branches  from  the  median 
to  the  middle  finger  and  the  thumb  side  of  the 
ring  finger.  25.  Ulnar  nerve.  26.  Branch  of 
the  same  nerve  to  the  flexor  profundus  digitorum. 
27.  (^^utaneous  and  anastomosing  filament  from 
the  ulnar.  28.  Dorsal  branch  of  this  nerve. 
2g.  .Superficial  palmar  branch.  30.  Common 
trunk  for  the  ring  and  little  fingers.  31.  Digital 
branch  to  the  internal  side  of  the  little  finger. 
32.  Deep  palmar  branch.  33.  Branches  from 
the  preceding  to  the  hypothenar  eminence.  34. 
Branches  to  the  fourth  interosseous  and  fourth 
lumbricales.     35.    Branches  to  the  same  in  the 


338  ULNAR    NERVE. 

the  biceps,  and,  as  it  descends  between  the  biceps  and  the 
brachialis  anticus,  it  suppHes  both.  Consequently,  if  the  nerve 
were  divided  in  the  axilla,  the  result  would  be  inability  to  bend 
the  arm.* 

In  one  hundred  arms  the  relative  position  of  the  nerve  to  the  artery  in  its 
course  down  the  arm  was  as  follows  :• — 

In  72,  the  nerve  took  the  ordinary  course. 

"    20,  the  nerve  crossed  obliquely  under  the  artery. 

"      5,  the  nerve  ran  parallel  and  superficial  to  the  artery. 

"  3,  the  ner\'e  ran  parallel  and  external  to  the  artery. 
These  varieties  of  the  median  nerve  are  of  practical  importance,  for  this 
reason :  Whenever  in  the  operation  of  tying  the  brachial  artery  we  do  not  find 
the  nerve  in  its  normal  position,  we  may  expect  to  find  some  irregular  distribution 
of  the  arteries  —  e.g.,  a  high  division  of  the  brachial,  or  even,  which  I  have  often 
seen,  a  '  vas  aberrans '  coming  from  the  upper  part  of  the  brachial,  and  joining 
either  the  radial  or  ulnar  arteries. 


Ulnar  Nerve.  —  This  nerve  arises  from  the  inner  cord  of 
the  brachial  plexus,  in  common  with  the  internal  cutaneous 
and  the  inner  head  of  the  median.  It  descends  along  the  inner 
side  of  the  brachial  artery,  as  far  as  the  insertion  of  the  coraco- 
brachialis.  The  nerve  then  diverges  from  the  artery,  running 
obliquely  over  the  inner  head  of  the  triceps,  perforates  ihe  in- 
ternal intermuscular  septum,  and  runs  with  the  inferior  profunda 
artery,  behind  the  internal  condyle  (Figs.  130,  131). 

The  distribution  of  the  iicjve  is  to  the  elbow-joint,  to  the 
flexor  carpi  ulnaris,  to  half  the  flexor  profundus  digltorum,  to 
all  the  interosseous  muscles  of  the  hand,  to  both  sides  of  the 
little  finger,  to  the  ulnar  side  of  the  ring  finger,  on  their  dorsal 
and  palmar  aspects,  to  the  muscles  of  the  ball  of  the  little 
finger,  to  the  wrist-joint,  to  the  two  ulnar  lumbricales,  and, 
lastly,  to  the  adductor  pollicis,  and  the  inner  head  of  the  flexor 
brevis  pollicis. 

Previous  to  the  examination  of  the  musculo-spiral  nerve  we 
should  examine  the  great  muscle  which  occupies  the  whole  of 
the  posterior  part  of  the  humerus  —  viz.,  the  triceps  extensor 
cubiti. 

*  In  some  instances  the  musculo-cutaneous  nerve  de.scends  on  the  inner  side 
of  the  coraco-brachialis  without  perforating  the  muscle ;  in  these  cases  it  often 
sends  a  larger  branch  than  usual  to  the  median  nerve. 

The  trunk  of  the  musculo  cutaneous  nerve  may  come  from  the  median  at  any 
point  between  the  axilla  and  the  middle  of  the  arm.  In  some  .^^ubjects  the  nerve 
is  alxsent ;  all  its  branches  are  then  supplied  by  the  median,  which  is  larger  than 
usual.  Such  anomalies  are  easily  explained  by  the  fact  of  the  two  nerves  having 
a  common  origin. 


TKicEi's  musclp:. 


339 


Triceps  Extensor  Cubiti. — ^This  muscle  has  three  dis- 
tinct origins,  named,  from  their  position,  the  external^  the  in- 
ternal, and  the  middle  or 
long  heads  ;  the  middle  or 
long  head  arises  by  a  flat 
tendon  from  the  axillary- 
border  of  the  scapula,  close 
to  the  glenoid  cavity,  and 
in  connection  with  the 
glenoid  and  capsular  liga- 
ments. The  external  head 
arises  from  the  humerus, 
beginning  in  a  pointed  form 
immediately  below  the  in- 
sertion of  the  teres  minor, 
from  the  posterior  surface 
between  this  and  the  mus- 
culo-spiral  groove,  and  from 
the  external  intermuscular 
septum.  The  internal  hea.d 
arises  from  the  humerus 
below  the  insertion  of  the 
teres  major,  from  the  pos- 
terior surface  of  the  bone 
below  the  musculo-spiral 
groove  and  from  the  in- 
ternal intermuscular  sep- 
tum. The  three  heads 
unite,  near  the  middle  of 
the  arm,  to  form  a  single 
fleshy  mass,  which  covers 
the  posterior  part  of  the 
elbow-joint,  and  is  inserted 
by  a  thick  tendon  into  the 
summit  and  sides  of  the 
olecranon.  There  is  a 
bursa  between  the  tendon 
and  the  olecranon,  which 
is  sometimes  multilocular. 
branch  from  the  musculo-spiral  nerve.* 

*  The  snianc-oneus,  a  small  muscle  situated  beneath  the  triceps,  will  be  de- 
.scribed  later  on. 


Fig.  132.  —  Triceps  Muscle. 


.  Triceps.  2.  Long  head  of  the  triceps.  3.  Outer 
head.  4.  Inner  head.  5.  Tendon  of  the  triceps.  6. 
Its  attachment  to  the  olecranon.  7.  Anconeus,  the 
fibres  of  which  follow  those  of  the  outer  head  of  the 
triceps.  8,  8.  Superior  part  of  the  deltoid  ;  the  poste- 
rior half  has  been  excised.  9.  Its  inferior  part.  10. 
Supra-spinatus.  11.  Infra-spinatus,  12.  Origin  of 
the  teres  minor.  13.  Insertion  of  the  teres  minor.  14. 
Teres  major.  15.  Superior  extremity  of  the  latissimus 
dorsi.  16.  Supinator  longus  or  brachio-radialis.  17. 
Extensor  carpi  radialis  longior.  18.  Extensor  carpi 
ulnaris,     19.    Flexor  carpi  ulnaris. 

Each  head  is  supplied  by  a  separate 


340  ISSECTION    OF    THE    FRONT    OF    THE    FOREARM. 

Musculo-spiral  Nerve.  —  This,  the  largest  of  the  brachial 
nerves,  arises,  in  common  with  the  circumflex,  from  the  poste- 
rior cord  of  the  brachial  plexus  (p.  322).  It  descends  at  first 
behind  the  third  portion  of  the  axillary  artery,  and  then  behind 
the  brachial  artery  ;  it  subsequently  winds  obliquely  round  the 
posterior  part  of  the  humerus,  between  the  external  and  inter- 
nal heads  of  the  triceps,  in  company  with  the  superior  profunda 
artery.  About  the  lower  third  of  the  outer  side  of  the  arm  the 
nerve  perforates  the  external  intermuscular  septum,  and  then 
runs  deeply  embedded  between  the  brachialis  anticus  and  the 
supinator  radii  longus  (or  brachio-radialis). 

The  nerve  gives  off  branches  on  the  itiner  side  of  the  humerus, 
to  the  inner  and  long  heads  of  the  triceps,  and  the  internal  cuta- 
neous branch  ;  on  the  back  of  the  humerus,  to  the  external  head 
of  the  triceps  and  the  anconeus  ;  on  the  outer  side  of  the  hume- 
rus, to  the  supinator  radii  longus  (or  brachio-radialis),  the  ex- 
tensor carpi  radialis  longior,  and  the  brachialis  anticus  (usually); 
lastly,  after  perforating  the  septum,  it  gives  off  the  upper  and 
lower  external  cutaneous  branches. 

A  little  above  the  elbow-joint  the  nerve  divides  into  two  prin- 
cipal branches — the  radial,  which  accompanies  the  radial  artery 
along  the  forearm,  and  \.\iQ  posterior  interosseous,  which  perforates 
the  supinator  brevis,  and  supplies  the  muscles  on  the  back  of 
the  forearm. 

To  sum  up  the  muscular  distribution  of  this  netve,  we  may 
say  that  it  supplies  all  the  extensors  of  the  forearm,  wrist, 
thumb,  and  fingers  ;  and  allt\\Q  supinators  except  one  —  namely, 
the  biceps  (supplied  by  the  musculo-cutaneous  nerve). 


DISSECTION  OF   THE   FRONT  OF  THE   FOREARIV 

Surface  Marking.  —  The  front  of  the  forearm  presents,  at 
the  bend  of  the  elbow,  a  triangular  depression,  from  which  there 
extends  down  to  the  wrist  a  groove  which  corresponds  to  the 
radial  artery  ;  on  the  inner  side  is  another  groove,  increasing 
in  depth  towards  the  wrist,  indicating  the  course  of  the  ulnar 
artery.  The  head  of  the  radius  can  be  easily  felt  on  the  outer 
side,  below  the  external  condyle  of  the  humerus,  and  in  the 
lower  third  the  bone  becomes  again  defined,  terminating  below 
in  the  styloid  process,  beyond  which  is  the  prominence  of  the 
tubercle  of  the  scaphoid.     The  border  of  the  ulna  can  be  felt  on 


CUTANEOUS    NERVES.  341 

the  inner  side  of  the  forearm,  in  the  lower  half,  and  it  ends  at 
the  wrist  in  an  ill-defined  styloid  process,  which  does  not  de- 
scend as  low  as  the  corresponding  process  of  the  radius.  The 
lower  part  of  the  forearm  presents,  an  inch  {2.§  cm.)  beyond  the 
wrist-joint,  a  transverse  furrow,  which  corresponds  with  the 
border  of  the  annular  ligament. 

Dissection.  —  Prolong  the  incision  down  to  the  wrist,  and, 
at  its  termination,  make  another  transversely.  Reflect  the  skin, 
and  dissect  the  subcutaneous  veins  and  nerves. 

Cutaneous  Veins.  —  On  the  inner  side  is  the  anterior  ulnar 
vein,  which  commences  on  the  front  of  the  wrist,  and  is  then 
continued  upwards  on  the  inner  side  of  the  forearm  as  far  as 
the  elbow,  where  it  is  joined  by  the  posterior  ulnar  vein  to  form 
the  common  ulnar  vein.  This  vein  communicates  with  the 
median  vein  by  numerous  branches  (p.  328). 

The  veins  on  the  back  of  the  hand  commence  at  the  extremi- 
ties of  the  fingers,  run  up  bctiuecn  the  knuckles,  and  unite  on 
the  back  of  the  hand,  forming  an  arch  with  its  concavity  up- 
wards. The  posterior  nlnar  vein  arises  from  this  arch  by  a 
branch  (vena  salvatella)  situated  over  the  fourth  interosseous 
space,  and  runs  up  on  the  back  of  the  forearm,  towards  the 
inner  condyle,  to  join  the  anterior  ulnar  vein. 

The  radial  vein,  situated  on  the  outer  side  of  the  forearm, 
commences  on  the  back  of  the  hand  from  the  venous  arch,  runs 
up  the  radial  side  of  the  front  of  the  forearm  to  the  elbow, 
where,  after  receiving  the  median  cephalic,  it  becomes  the  ce- 
phalic vein. 

Running  up  in  front  of  the  middle  of  the  forearm  is  the 
median  vein  ;  it  communicates  in  the  forearm  with  the  radial 
and  anterior  ulnar  veins,  and  near  the  bend  of  the  elbow  it  is 
joined  by  a  deep  branch  —  mediana  profunda  —  after  which  it 
divides  into  two  branches,  an  outer  or  median  cephalic,  which 
joins  the  cephalic,  and  an  inner  or  median  basilic,  which  joins 
the  basilic  (Fig.  127,  p.  327). 

Cutaneous  Nerves.  —  On  the  radial  side  of  the  forearm,  as 
low  down  as  the  wrist,  are  found  the  terminal  filaments  of  the 
anterior  branch  of  the  musculo-cutaneous  nerve,  which,  about 
the  middle  of  the  forearm,  sends  2.  posterior  branch  backwards  to 
supply  the  posterior  and  lower  part  of  the  forearm  as  low  as  the 
wrist,  communicating  with  the  radial  and  external  cutaneous 
branch  of  the  musculo-spiral.  At  the  lower  part  of  the  front 
of  the  forearm,  one  or  more  of  these  filaments  are  situated  over 


342  DEEP  FASCIA  OF  THE  FOREARM. 

the  radial  artery,  and  one  branch  passes  to  the  pahn  to  supply 
the  skin  over  the  muscles  of  the  ball  of  the  thumb  ;  it  commu- 
nicates with  the  palmar  branch  of  the  median  and  with  the 
radial  nerve. 

In  front  of  the  upper  part  of  the  forearm  are  some  filaments 
of  the  external  eutaneoiis  brancJi  of  the  musculo-spiral  nerve  ; 
on  the  outer  and  back  part  of  the  forearm,  near  the  elbow,  the 
lower  exfenial  cutaneous  h'anch  of  the  musculo-spiral  runs  down 
as  far  as  the  wrist  to  supply  the  skin. 

At  the  lower  third  of  the  radial  side  of  the  forearm,  the  radial 
neii.>e  becomes  superficial,  and  turns  over  the  radius  to  supply 
the  back  of  the  hand  and  fingers. 

On  the  ulnar  side  the  ajiterior  division  of  the  internal  cutane- 
ous nerve  descends  as  far  as  the  wrist,  its  posterior  branch  pass- 
ing the  back  of  the  forearm  to  supply  it  as  far  as  the  middle. 
Near  the  styloid  process  of  the  ulna,  the  dorsal  branch  of  the 
ulnar  ner\^e  perforates  the  fascia  to  reach  the  back  of  the 
hand. 

Deep  Fascia  of  the  Forearm.  —  The  muscles  of  the  fore- 
arm are  enveloped  by  a  dense  shining  aponeurosis,  continuous 
with  that  of  the  arm.  Its  thickness  increases  towards  the  wrist, 
that  the  tendons,  in  this  situation,  may  be  kept  in  their  position. 
It  is  composed  of  fibres  which  cross  each  other  obliquely,  and 
is  attached,  above,  to  the  condyles  of  the  humerus  and  olecra- 
non ;  internally,  to  the  ridge  on  the  posterior  part  of  the  ulna. 
At  the  back  of  the  wrist  it  forms  the  posterior  annular  ligament, 
and  in  front  it  is  continuous  with  the  anterior  annular  ligament. 
Above,  the  fascia  is  strengthened  by  fibres  from  the  tendons  of 
the  biceps  and  brachialis  anticus.  The  aponeurotic  expansion 
from  the  inner  edge  of  the  tendon  of  the  biceps  is  exceedingly 
strong.  It  braces  the  muscles  on  the  inner  side  of  the  forearm, 
and  interlaces  at  right  angles  with  the  fibres  of  the  fascia  at- 
tached to  the  internal  condyle.  The  under  surface  of  the  fascia 
gives  origin  to  the  muscular  fibres  in  the  upper  part  of  the  fore- 
arm, and  furnishes  septa  which  separate  the  muscles,  and  form 
surfaces  for  their  origin.  The  fascia  is  perforated  at  various 
parts  for  the  passage  of  the  cutaneous  vessels  and  nerves  of 
the  forearm. 

Dissection.  —  Remove  the  fascia  from  the  muscles  by  incis- 
ions corresponding  to  those  for  reflecting  the  skin,  taking  care 
of  the  cutaneous  branches  of  the  median  and  ulnar  nerves  close 
to  the  wrist. 


MUSCLES  OF  THE  FOREARM.  343 

Triangle  at  the  Elbow.  —  At  the  bend  of  the  elbow  is 
a  triangular  space,*  with  its  base  towards  the  humerus  ;  on 
the  inner  side  this  space  is  bounded  by  the  pronator  teres  ;  on  the 
outer,  by  the  supinator  radii  longus  or  brachio-radialis.  In  it 
are  the  following  objects  which  must  be  carefully  dissected  : 
I,  In  the  centre  is  the  brachial  artery  (with  its  companion  veins) 
dividing  into  the  radial  as  its  outer,  and  into  the  ulnar  as  its 
inner  branch  ;  2,  on  the  outer  side  of  the  artery  is  the  tendon 
of  the  biceps  ;  3,  on  the  inner  side  is  the  median  nerve  ;  4,  the 
musculo-spiral  nerve  on  the  outer  side  is  partly  concealed  by  the 
supinator  longus  or  brachio-radialis  ;  5,  the  radial  recurrent 
artery ;  6,  the  anterior  ulnar  recurrent ;  7,  the  common  interos- 
seous branch  of  the  ulnar  artery  ;  8,  the  vena  mediana  pro- 
funda. 

Muscles  of  the  Forearm.  —  The  muscles  of  the  forearm 
are  arranged  in  two  groups  :  one,  consisting  of  supinators  and 
extensors,  is  attached  to  the  outer  condylar  ridge  and  condyle  ; 
the  other,  consisting  of  pronator  and  flexors,  is  attached  to  the 
inner  condyle.  The  inner  group  should  be  examined  first. 
They  arise  by  a  common  tendon,  and  are  arranged  in  the  follow- 
ing order  :  pronator  teres  ;  flexor  carpi  radial  is;  palmaris  longus; 
flexor  sublimis  digitorum,  and  flexor  carpi  ulnaris. 

Pronator  Radii  Teres.  —  This  muscle  forms  the  inner 
boundary  of  the  triangular  space  at  the  elbow.  It  arises  by  two 
heads  ;  one,  from  the  anterior  surface  of  the  internal  condyle, 
from  the  common  tendon,  from  the  fascia  of  the  forearm,  and 
from  the  septum  between  it  and  the  flexor  carpi  radialis  ;  the 
other,  by  a  small  tendinous  origin  from  the  inner  border  of  the 
coronoid  process  of  the  ulna.  From  these  two  origins,  between 
which  the  median  nerve  passes,  the  muscle  proceeds  obliquely 
downwards  and  outwards  across  the  forearm,  and  is  inserted  by 
a  flat  tendon  into  a  rough  surface  on  the  outer  and  back  part  of 
the  middle  third  of  the  radius.  In  amputating  the  forearm  it  is 
very  desirable  to  save  the  insertion  of  this  muscle,  that  the 
stump  may  have  a  pronator.       Its  nerve  comes  from  the  median 

(Fig.  133)- 

Flexor  Carpi  Radialis.  —  This  muscle,  situated  on  the  ulnar 
side  of  the  preceding  muscle,  arises  by  the  common  tendon 
from  the  internal  condyle,  from  the  intermuscular  septa,  and 
from  the  fascia  of  the  forearm.  The  fleshy  fibres  terminate  a 
little  above   the  middle  of  the   forearm,  in  a  flat  tendon,  which 

*  Anticupital  space. 


344 


MUSCLES    OF    THE    FOREARM. 


runs  in  a  separate  sheath  outside  the  anterior  annular  ligament 
of  the  wrist,  passes  through  a  groove  in  the  os  trapezium, 
bridged  over  by  fibrous  tissue  and  lined  by  a  synovial  membrane. 


1.  Inferior  part  of  the  biceps. 

2.  Aponeurosis  of  the  biceps. 

3.  Tendon  by  which  it  is  at- 

tached   to    the  bicipital 
tuberosit)'  of  the  radius. 

4.  4.    Brachialis  anticus. 

5.  Internal    head   of    the  tri- 

ceps. 

6.  Pronator  radii  teres. 

7.  Flexor  caroi  radialis. 

8.  Palmaris  longus. 

9.  Inferior  extremity  of   this 

muscle  expanding  into  the 
palmar  fascia. 

10.  Flexor  carpi  ulnaris. 

1 1 .  The  attachment  to  the  pisi- 

form bone. 

12.  Supinator    longus    or   bra 
chio-radialis. 

Inferior  attachment  of  this 

muscle. 
14.    Extensor  carpi  radialis 

longior. 
Extensor      carpi     radialis 

brevior. 
16.   Extensor    ossis    metacarpi 

pollicis. 


13 


15 


17.  Tendon  of  the  same  in- 
serted into  the  metacar- 
pal bone. 

18.  Tendon  of  the  extensor 
secundi  intemodii  polhcis. 

19,  19.  Flexor  sublimis  digito- 
rum. 

20,  20.  Tendons  of  insertion 
di\nding  to  allow  the  ten- 
dons of  the  flexor  profun- 
dus digitorum  to  pass  to 
their  insertion. 

31,  21.  Insertion  of  the  flexor 
sublimis  digitorum  to  the 
lower  part  of  the  middle 
phalanges. 

22.  22.  Attachment  of  the 
flexor  profundus  digito- 
rum to  the  distal  pha- 
langes. 

23.  23.   Lumbricales. 

24.  Abductor  pollicis. 

25.  Its  attachment  to  the  proxi- 
mal phalanx  of  the  thumb. 

26.  26.    Flexor  longus  pollicis. 

27.  Flexor  bre%'is  digitorum. 

28.  Abductor  minimi  digiti. 


HYZlLtS  del. 

Fic.  133.  —  SuPERPiciAL  Muscles  on  the  Anterior  Surface  of  the  Left  Forearm. 

and  is  inserted  \v\\.o  the  base  of  the  metacarpal  bone  of  the  index 
finger.     The  outer  border  of  its  tendon  is  the  guide  to  the  radial 


MUSCLES    OF    THE    FOREARM.  345 

artery  in  the  lower  half  of  the  forearm.      Its  nen^e  comes  from 
the  median*  (Fig.  133). 

It  acts  as  a  flexor  of  the  wrist,  including  not  only  the  joint 
proper,  but  also  the  carpo-metacarpal  joints.  Slight  pronation 
can  be  excited  when  the  hand  is  thoroughly  supined.      (A.  H.) 

Palmaris  Longus.  —  This  slender  muscle  arises  from  the 
common  tendon  at  the  internal  condyle,  from  the  intermuscular 
septum,  and  from  the  fascia  of  the  forearm.  About  the  middle 
of  the  forearm  it  terminates  in  a  fiat  tendon,  which  descends 
along  the  middle  of  the  forearm  to  the  wrist,  lying  upon  the 
flexor  sublimis  digitorum;  it  then  passes  over  the  anterior  an- 
nular ligament,  and  is  continued  into  the  palmar  fascia.  This 
muscle  is  a  tensor  of  the  palmar  fascia.f  Its  nerve  comes  from 
the  median  (Fig.  133). 

Flexor  Carpi  Ulnaris.  —  This  muscle  arises  by  two  heads  : 
one  from  the  internal  condyle,  the  common  tendon,  and  the  in- 
termuscular septum  ;  the  other  from  the  inner  edge  of  the 
olecranon  :  these  two  origins  form  an  arch,  under  which  the 
ulnar  nerve  and  the  posterior  ulnar  recurrent  artery  pass.  It 
also  arises  from  the  upper  two-thirds  of  the  posterior  edge  of 
the  ulna,  through  the  medium  of  the  aponeurosis,  which  is  com- 
mon to  this  muscle,  the  flexor  profundus  digitorum,  and  the 
extensor  carpi  ulnaris.  The  tendon  appears  on  the  radial  side 
of  the  muscle,  about  the  lower  third  of  the  forearm,  and  receives 
fleshy  fibres  on  its  ulnar  side  as  low  as  the  wrist.  It  is  inserted 
into  the  pisiform  bone,  and  thence  by  a  strong  tendon  into  the 
unciform  and  the  base  of  the  fifth  metacarpal  bone.  Its  7ierve 
comes  from  the  ulnar  (Fig.   133). 

The  tendon  of  the  flexor  carpi  ulnaris  is  the  guide  to  the  ulnar 
artery,  which  lies  close  to  its  radial  side,  and  is  overlapped  by  it. 
As  it  passes  over  the  annular  ligament,  the  tendon  furnishes  a 
fibrous  expansion  to  protect  the  ulnar  artery  and  nerve.  Its 
action  is  as  a  flexor  of  the  wrist.  It  will  straighten  the  hand 
when  abducted  ;   i.e.,  slight-adductor. 

Flexor   Sublimis    Digitorum.  —  This  muscle  has  three  dis- 

*  A  muscle  is  not  infrequently  found  beneath  this  muscle,  called  by  Mr.  Wood 
the  flexor  carpi  radialis  brevis,  or  profundus.  It  arises  from  the  front  of  the  radius 
above  the  pronator  quadrat  us,  and  is  inserted  into  the  base  of  the  metacaipal  bone 
of  the  middle  finger.      [Journ.  of  Anat.  and  Phys.,  p.  55,  Nov.  1S66.) 

t  The  palmaris  longus  is  absent  in  about  one  out  often  subjects.  The  situa- 
tion of  its  muscular  portion  is  subject  to  variation,  sometimes  occupying  the  mid- 
dle, sometimes  the  lower  third  of  the  forearm.  The  tendon  is  in  some  instances 
wholly  inserted  into  the  anterior  annular  ligament. 


546 


MUSCLES    OF    THE    FOREARM. 


tinct  origins,  and  is  situated  beneath  those  previously  mentioned, 
so  that,  in  order  to  expose  it  fully,  the  preceding  muscles  should 
be  reflected  by  cutting  them  through  the  middle,  and  turning  the 


Flexor  sublimis  digito- 
rum. 

Its  origin  from  the  inter- 
nal condyle.  -^^ 

Its  origin  from  the 
coronoid  process. 

4.  Its  origin  from  the 
radius. 

5.  Its  two  superficial  ten- 
dons to  the  middle  and 
ring  fingers. 

6.  Its  two  deep  tendons 
to  the  index  and  little 
fingers. 

Flexor  longus  pollicis. 
Tendon  of  this  nuiscle. 
Bifurcation  of  the  tendons 

of    the     flexor    longus 

digitorum. 

10.  Groove  made  by 
these  tendons. 

11.  Tendons  of  tlie 
flexor  profundus  digi- 
torum occupying  these 
grooves  and  filling 
them  up. 


12.  Brachialis     anticus    ten- 

don. 

13.  Internal  condyle  of  the 

humerus. 

14.  Biceps  tendon. 

15.  Supinator      longus       or 

brachio-radialis. 

16.  Its     attachment     to     the 

styloid  process  of    the 
radius. 

17.  Extensor    carpi    radialis 

longior. 

18.  Tendon    of   insertion    of 

the  pronator  radii  teres. 

ig.   Tendon    of    insertion    of 

the  flexor  carpi  radialis. 

20.  Triceps. 

21.  Flexor  carpi  ulnaris. 

22.  Its     attachment    to     the 

pisiform  bone. 

23.  Abductor  minimi  digiti. 

24.  Flexor     brevis      minimi 

digiti. 
23.   Abductor  pollicis. 


Fir,.  134. —  Flexor  Muscles  op  the  Fincers. 


ends  upwards  and  downwards.  The  first  or  longer  otigin  takes 
place  from  the  internal  condyle,  from  the  internal  lateral  liga- 
ment, the  common  tendon,  and  the  intermuscular  septum  ;  the 


RADIAL    ARTERY.  347 

second  origin  takes  place  from  the  coronoid  process  o.  the  uhia 
above  the  pronator  teres  ;  the  third  origin,  by  tendinous  and 
fleshy  fibres  from  the  oblique  ridge  on  the  front  of  the  radius, 
extending  from  the  tubercle  to  about  an  inch  {2.^  cm.)  below 
the  insertion  of  the  pronator  teres.  This  third,  called  its  radial 
origin,  is  partly  concealed  by  the  pronator  teres.  The  muscle, 
thus  formed,  passes  down  the  middle  of  the  forearm,  and  divides 
into  four  distinct  muscular  slips  ;  from  these,  four  tendons  arise, 
which  pa^s  beneath  the  annular  ligament,  arranged  in  two  pairs, 
the  tendons  of  the  middle  and  ring  fingers  being  placed  over 
those  of  the  fore  and  little  fingers.  The  tendons  pass  through 
the  palm  to  the  fingers,  where  they  diverge  and  split  to  allow 
the  passage  of  the  deep  flexor  tendons,  and  are  inserted  into  the 
sides  of  the  second  phalanges  where  they  will  be  subsequently 
traced.  Its  action  is,  therefore,  to  bend  the  second  joint  of  the 
fingers  and  continuing  its  contraction  will  assist  to  flex  the 
wrist  (Fig.  134). 

The  muscles  described  as  atising  from  the  internal  condyle 
are  all  supplied  by  the  median  nerve,  except  the  flexor  carpi 
ulnaris,  which  is  supplied  by  the  ulnar. 

Having  finished  the  superficial  muscles  on  the  inner  side  of 
the  forearm,  notice  one  of  those  on  the  outer  side,  named  supi- 
nator radii  longus,  before  tracing  the  vessels  and  nerves  of  the 
forearm. 

Supinator  Radii  Longus,  or  Brachio-radialis.  —  This 
muscle  forms  the  external  boundary  of  the  triangular  space*  at 
the  bend  of  the  elbow.  It  arises  by  fleshy  fibres  from  the  up- 
per two-thirds  of  the  external  condylar  ridge  of  the  humerus, 
commencing  a  little  below  the  insertion  of  the  deltoid,  and  from 
the  external  intermuscular  septum.  The  muscular  fibres  termi- 
nate about  the  middle  of  the  forearm  in  a  flat  tendon,  which 
is  inserted  into  the  outer  side  of  the  base  of  the  styloid  process 
of  the  radius.  The  inner  border  of  the  muscle  is  the  guide  to 
the  radial  artery,  which  lies  between  this  muscle  and  th-e  flexor 
carpi  radial  is.  It  supinates  the  hand,  but  acts  much  more  pow- 
erfully as  a  flexor  of  the  forearm.  It  is  siipplied  by  the  musculo- 
spiral  nerve  (Fig.  134). 

Radial  Artery.  —  The  radial  artery,  the  smaller  division  of 
the  brachial,  runs  down  the  radial  side  of  the  forearm  to  the 
wrist,  where  it  turns  over  the  external  lateral  ligament  of  the 
carpus,  beneath  the  extensor  tendons  of  the  thumb,  and  sinks 

*  Atiticupital  space. 


348  BRANCHES    OF    THE    RADIAL    ARTERY. 

into  the  angle  between  the  first  and  second  metacarpal  bones  to 
form  the  deep  palmar  arch.  Thus,  its  course  corresponds  with 
a  line  drawn  from  the  middle  of  the  bend  of  the  elbow  to  the 
front  of  the  styloid  process  of  the  radius. 

In  the  upper  third  of  the  forearm,  the  artery  lies  deep  between 
the  pronator  teres  on  the  inner  and  the  brachio-radialis  on  the 
outer  side ;  the  fleshy  border  of  the  latter  overlaps  it  in  muscu- 
lar subjects.  In  the  lower  two-thirds  of  the  forearm  the  artery 
is  more  superficial,  and  is  placed  between  the  tendons  of  the 
brachio-radialis  on  the  outer  and  the  flexor  carpi  radialis  on  the 
inner  side.  In  its  course,  it  lies  successively  on  the  following  : 
first,  upon  the  tendon  of  the  biceps  ;  secondly,  upon  the  supina- 
tor radii  brevis  ;  thirdly,  upon  the  insertion  of  the  pronator 
teres ;  fourthly,  upon  the  radial  origin  of  the  flexor  sublimis ; 
fifthly,  upon  the  flexor  longus  pollicis  ;  sixthly,  upon  the  prona- 
tor quadratus,  and  lastly,  upon  the  lower  end  of  the  radius. 
The  artery  then  turns  round  the  outer  side  of  the  wrist-joint, 
lying  upon  the  external  lateral  ligament,  and  covered  by  the 
tendons  of  the  extensores  ossi  metacarpi  and  extensor  brevis 
pollicis  or  primi  internodii  pollicis,  some  cutaneous  veins,  and 
branches  of  the  radial  nerve  ;  next,  it  lies  upon  the  trapezium  ; 
it  is  then  crossed  by  the  extensor  longus  pollicis  or  secundi  in- 
ternodii pollicis  ;  and,  lastly,  passing  between  the  two  heads  of 
the  first  dorsal  interosseous  muscle,  it  enters  the  palm  to  form 
the  deep  palmar  arch.  It  is  accompanied  by  two  veins,  which 
communicate  at  frequent  intervals,  and  join  the  venae  comites  of 
the  brachial  artery  at  the  bend  of  the  elbow. 

In  the  middle  third  of  its  course  the  artery  is  accompanied 
by  the  radial  nerve  (a  branch  of  the  musculo-spiral),  which  lies 
to  its  outer  side.  Below  this  point,  the  nerve  leaves  the  artery 
and  passes,  under  the  tendon  of  the  brachio-radialis,  to  the  back 
of  the  hand. 

Thus,  in  the  situation  where  the  pulse  is  usually  felt,  the  radial 
nerve  no  longer  accompanies  the  artery  ;  nevertheless,  the  vessel 
is  accompanied  by  a  branch  of  the  musculo-cutaneous  (or  exter- 
nal cutaneous),  which  lies  superficially  to  it. 

The  radial  artery  sends  off  in  the  forearm  the  following 
branches,  besides  offsets,  which  supply  the  muscles  on  the  outer 
side  of  the  forearm  — 

a.  The  radial  recurrent  is  given  off  just  below  the  elbow;  it  ascends  upon  the 
supinator  brevis,  between  the  brachio-radialis  and  the  brachialis  anticus,  to  supply 
the  long  and  short  supinators  and  the  two  radial  e.\tensors.     It  runs  up  with  the 


ULNAR    ARTERY.  349 

musculo-spiral  nerve,  and   foiTns  a  delicate  inosculation  with  the  superior  profunda 
(Fig.  129,  p.  334). 

b.  The  muscular  branches  which  are  given  off  to  the  muscles  on  the  outer  side 
of  the  forearm. 

c.  The  arteria  siiperficialis  voice  arises  from  the  radial,  about  half  an  inch  (/j 
mm.)  or  more  above  the  lower  end  of  the  radius  ;  it  runs  over  the  anterior  annular 
ligament,  above  or  through  the  origin  of  the  muscles  of  the  ball  of  the  thumb, 
into  the  palm  of  the  hand,  where  it  sometimes  inosculates  with  the  superficial 
branch  of  the  ulnar,  and  completes  the  superficial  palmar  arch.*  t 

d.  Thu anlerior  carpal  artery  is  a  small  branch  of  the  radial,  which  arises  close 
to  the  lower  border  of  the  pronator  quadratus,  and  then  runs  beneath  the  tendons, 
and  supplies  the  anterior  surface  of  the  synovial  membrane  and  bones  of  the  car- 
pus, anastomosing  with  the  anterior  interosseous,  the  anterior  carpal  branch  of  the 
ulnar,  and  the  recurrent  carpal  branch  of  the  deep  palmar  arch. 

At  the  wrist  it  gives  off  — 

e.  The  posterior  carpal  artery,  which  runs  beneath  the  extensor  tendons,  and 
joins  the  corresponding  branch  of  the  ulnar  to  form  an  arch;  it  also  anastomoses 
with  the  anterior  interosseous  arteiy  on  the  back  of  the  wrist. 

Radial  Nerve.  — The  radial  nerve,  a  branch  of  the  musculo- 
spiral,  is  given  off  above  the  bend  of  the  elbow,  deep  between 
the  brachio-radialis  and  brachialis  anticus  ;  it  descends  on  the 
outer  side  of  the  radial  artery,  covered  by  the  brachio-radialis. 
In  the  upper  \\{\x^  of  ths  forearm,  the  nerve  is  at  some  distance 
from  the  artery ;  in  the  middle  third,  it  approaches  nearer  to  it, 
lying  to  its  outer  side ;  but  in  the  lotver  third,  the  nerve  leaves 
the  artery,  passes  underneath  the  tendon  of  the  brachio-radialis, 
perforates  the  deap  fascia  on  the  outer  side  of  the  forearm,  and 
becomes  subcutaneous.  It  then  divides  into  two  branches  :  an 
outer,  the  smaller,  which  supplies  the  skin  of  the  ball  of  the 
thumb,  and  communicates  with  the  anterior  branch  of  the 
musculo-cutaneous  nerve;  and  an  inner,  which  generally  sup- 
plies both  sides  of  the  dorsal  aspects  of  the  thumb,  of  the  index 
and  middle  fingers,  and  of  the  radial  side  of  the  ring  finger. 

Ulnar  Artery.  —  This  artery,  the  larger  of  the  two  divisions 
of  the  brachial,  comes  off  below  the  elbow,  runs  obliquely  in- 
wards along  the  ulnar  side  of  the  forearm  to  the  wrist,  passes 
over  the  annular  ligament  near  the  pisiform  bone,  and,  entering 
the  palm,  forms  the  superficial  palmar  arch,  by  inosculating  with 
the  superficialis  volae  (Fig.   129,  p.  334). 

*  TTiere  is  great  variety  in  the  size  and  origin  of  the  superficialis  volas ;  some- 
times it  is  very  large,  arises  higher  than  usual,  and  runs  to  the  wrist  parallel  with 
the  radial ;  sometimes  it  is  very  small,  terminating  in  the  muscles  of  the  thumb ; 
or  it  may  be  absent. 

t  When  this  artery  arises  from  the  radial  two  inches  (5  cm)  or  more  above 
the  distal  end  of  the  radius,  it  continues  parallel  with  the  radial  artery,  thus  pro- 
.ducing  the  condition  known  zs,  double  pulse.     (A.  H.) 


350 


ULNAR  ARTERY. 


In  the  upper  hau  of  its  course  the  artery  describes  a  gentle 
curve  with  the  concavity  towards  the  radius,  and  lies  deep  be- 
neath the  superficial  layer   of  muscles,    namely,   the    pronator 


l[| 


112 


112 


Trunk  of  the  radial  nerve. 

Its  branch  to  brachio- 
radialis. 

Its  branch  to  extensor  car- 
pi radialis  longior. 

Its  branch  to  extensor  car- 
pi radialis  brevior. 

Bifurcation  of  the  trunk. 

Posterior  or  muscular 
branch. 

The  same  branch  travers- 
ing the  supinator  brevis 
and  supplying  it. 


8.  Terminal  filaments  of  this 

division. 

9,  g.   Anterior    or    cutaneous 

branch  of  this  nerve. 

10.  Termination    of  this 

branch . 

11.  Musculo-cutaneous  n. 

12.  Its  terminal  divisions. 

13.  Anastomosing  branch  with 

the  cutaneous  division  of 
the  radial 


Fig.  135.  —  Terminal  Braiichrp  of  the  Radial  Nhrvk. 


teres,  flexor  carpii  radialis,  palmaris  longus,  and  flexor  sublimis 
digitorum.  It  is  also  crossed  in  its  upper  part  by  the  median 
nerve.     In  the  lower  part  of  its  course  it  comes  nearer  the  sur- 


ULNAR    NERVE.  35  I 

face,  and  descends  between  the  flexor  sublimis  and  flexor  carpi 
ulnaris,  of  which  the  tendon  partially  overlaps  it  at  the  wrist. 
The  artery  lies  for  a  short  distance  on  the  brachialis  anticus ; 
in  the  remainder  of  its  course  it  lies  on  the  flexor  profundus 
digitorum. 

The  ulnar  nerve  is  at  first  separated  from  the  artery  by  a  con- 
siderable interval ;  about  the  middle  of  the  forearm  it  joins  the 
artery,  and  accompanies  it  in  the  rest  of  its  course,  lying  close 
to  its  inner  side.  Both  pass  over  the  anterior  annular  ligament 
of  the  carpus,  lying  close  to  the  pisiform  bone,  —  the  nerve  be- 
ing nearer  to  the  ulnar  side  and  a  little  behind  the  artery.  A 
strong  expansion  from  the  tendon  of  the  flexor  carpi  ulnaris 
protects  them  in  this  exposed  situation. 

Observe  that  the  ulnar  artery,  in  the  lower  third  of  its  course, 
lies  under  the  radial  border  of  the  tendon  of  the  flexor  carpi 
ulnaris,  which  is  the  surgical  guide  to  the  vessel.  The  artery 
is  accompanied  by  two  veins,  which  join  the  venae  comites  of 
the  brachial. 

The  ulnar  artery  gives  off  the  following  branches  in  the  fore- 
arm :  — 

a.  The  anterior  ami  posterior  jilnar  recurrejit  arteries  arise  immediately  below 
the  elbow-joint  —  sometimes  by  a  common  trunk.  The  a«/^r/(7r  passes  upwards 
between  the  brachiaUs  anticus  and  the  pronator  teres,  and  inosculates  w^th  the 
inferior  profunda  and  anastomotica  magna.  The  posterior,  the  larger,  ascends 
between  the  flexor  sublimis  and  the  flexor  profundus  digitorum,  to  the  space 
between  the  internal  condyle  and  the  olecranon  :  it  then  passes  up  between  the  two 
heads  of  the  flexor  carpi  ulnaris,  where  it  inosculates  wnth  the  inferior  profunda, 
the  anastomotica  magna,  and,  above  the  olecranon,  with  the  posterior  interosseous 
recurrent  (Fig.   129,  p.  334). 

b.  The  common  interosseous  artery  is  about  half  an  inch  (/^.j-  mm.)  long.  It 
arises  from  the  ulnar,  just  below  the  tubercle  of  the  radius,  and  soon  divides  into 
the  anterior  and  posterior  interosseous,  which  we  shall  examine  presently. 

c.  The  muscular  branches,  which  supply  the  muscles  on  the  ulnar  side  of  the 
forearm. 

d.  The  carpal  branches  are  given  off  just  above  the  pisiform  bone  ;  the  posterior 
carpal  runs  beneath  the  tendon  of  the  flexor  carpi  ulnaris  and  the  extensor  ten- 
dons, and  forms,  with  the  corresponding  branch  of  the  radial  artery,  an  arch,  from 
which  are  usually  given  off  the  second  and  third  dorsal  interosseous  arteries  :  these 
anastomose  with  the  perforating  arteries.  The  anterior  carpal  runs  in  front  of  the 
carpus,  beneath  the  flexor  tendons,  supplies  the  synovial  membrane  and  the  liga- 
ments, and  anastomoses  with  the  anterior  carpal  from  the  radial. 

Ulnar  Nerve.*  —  This  nerve  runs  behind  the  internal  con- 
dyle, between  two  origins  of  the  flexor  carpi  ulnaris.  In  its 
course  down  the  ulnar  side  of  the  upper  part  of  the  forearm,  the 

*  The  ulnar  nerve,  like  the  median,  is  only  distributed  to  structures  below  the 
elbow-joint.  —  A.  H. 


352  MEDIAN    NERVE. 

nerve  is  still  covered  by  this  muscle,  and  lies  upon  the  flexor 
profundus  digitorum.      About   the   middle   of  the  forearm,   the 
nerve  joins  the  ulnar  artery,  and  runs  along  its  inner  side  over 
the  anterior  annular  ligament  into  the  palm  (Fig.  131,  p.  337). 
The  ulnar  nerve  gives  off  the  following  branches  :  — 

a.  The  articular  branches  to  the  joint  are  given  off  to  it,  immediately  behind  the 
elbow. 

b.  The  muscular  branches  are  distributed  to  the  flexor  carpi  ulnaris  and  the 
iilnar  half  of  the  flexor  profundus  digitorum,  and  are  given  off  from  the  ulnar  a 
short  distance  below  the  elbow. 

c.  A  cutaneous  brattck  is  given  off  about  the  middle  of  the  forearm,  one  fila- 
ment of  which,  called  the  palmar  cutaneotts  branch,  accompanies  the  ulnar  artery 
to  the  palm,  and  communicates  with  branches  from  the  median  nerve. 

d.  The  dorsal  cutaneous  branch,  of  considerable  size,  is  given  off  from  the  ulnar 
about  two  inches  above  the  styloid  process  of  the  ulna  to  pass  to  the  back  of  the 
hand.  It  crosses  under  the  tendon  of  the  flexor  carpi  ulnaris,  pierces  the  deep 
fascia,  and,  immediately  below  the  styloid  process  of  the  ulna,  appears  on  the 
back  of  the  hand,  wher6  it  divides  into  branches  which  supply  the  back  of  the 
little  finger  and  half  of  the  ring  finger ;  here  also  it  sends  a  branch  which  com- 
municates with  the  corresponding  branch  of  the  radial  nerve. 

e.  Articular  branches  are  also  distributed  to  the  wrist-joint, 

IVIedian  Nerve.  — This  nerve,  at  the  bend  of  the  elbow,  lies 
on  the  inner  side  of  the  brachial  artery  and  beneath  the  bicipital 
fascia.  It  then  passes  between  the  two  heads  of  origin  of  the 
pronator  teres,  and  descends  along  the  middle  of  the  forearm, 
between  the  flexor  sublimis  and  the  flexor  profundus  digitorum. 
At  the  lower  part  of  the  forearm,  it  becomes  more  superficial, 
lying  above  the  wrist  between  the  outer  tendon  of  the  flexor 
sublimis  and  the  inner  border  of  the  tendon  of  the  flexor  carpi 
radialis ;  beneath,  or  to  the  ulnar  side  of  the  palmaris  longus, 
and  having  in  front  of  it  the  skin  and  deep  fascia ;  it  then 
enters  the  palm  beneath  the  anterior  annular  ligament,  and 
divides  into  five  branches  for  the  supply  of  the  thumb,  both  sides 
of  the  fore  and  middle  fingers,  and  the  radial  side  of  the  ring 
finger  (Fig.  131,  P-  337)- 

Immediately  below  the  elbow,  the  median  nerve  sends  off :  — 

a.  The  muscular  branches  to  the  pronater  teres,  and  to  all  the  flexor  muscles 
of  the  forearm,  except  the  flexor  carpi  ulnaris  and  the  ulnar  half  of  the  flexor  pro- 
fundu.s,  which  are  supplied  by  the  ulnar  nerve. 

b.  The  anterior  interosseous  tierve,  also  a  branch  of  the  median,  runs  with  the 
anterior  intero-sseous  artery  on  the  interosseous  membrane,  lying  on  its  radial  side, 
between  the  flexor  longus  pollicis  and  flexor  profundus  digitorum  ;  it  supplies  both 
these  mu-scles  and  the  pronator  quadratus. 

c.  Tha  pahnar  ctttafteous  braiich  is  given  off  from  the  median  before  it  passes 
beneath  the  annularligament.  This  branch  passes  over  the  ligament  and  divides 
into  numerous  filaments  to  supply  the  skin  of  the  palm  and  the  ball  of  the  thumb, 
communicating  with  the  cutaneous  palmar  branches  of  the  ulnar,  the  external  cu- 
taneous, and  the  radial  nerves. 


DEEP    MUSCLES     OF    THE    FOREARM.  353 

Dissection.  —  Now  reflect  the  superficial  layer  of  muscles  to 
see  those  more  deeply  seated.  Preserve  the  principal  vessels 
and  nerves. 

The  deep-seated  muscles  are,  on  the  ulnar  side,  the  flexor 
digitorum  profundus  ;  and,  on  the  radial  side,  the  flexor  longus 
pollicis  ;  beneath  both,  near  the  wrist,  lies  a  transverse  muscle, 
the  pronator  quadratus.  On  the  interosseous  membrane,  be- 
tween the  first  two  named  muscles,  run  the  anterior  interosse- 
ous artery  and  nerve. 

Flexor  Profundus  Digitorum.  —  This  is  the  thickest  muscle 
of  the  forearm.  It  arises  from  the  upper  two-thirds  of  the  an- 
terior surface  of  the  ulna,  surrounding  the  insertion  of  the 
brachial  anticus  above,  from  the  same  extent  of  its  internal 
surface,  from  the  aponeurosis  attached  to  the  posterior  edge  of 
the  ulna,  and  from  the  ulnar  two-thirds  of  the  interosseous  mem- 
brane (Fig  136).  About  the  middle  of  the  forearm  the  muscle 
is  inserted  into  four  flat  tendons,  of  which  only  that  which  goes 
to  the  index  finger  is  separate  from  the  others  above  the  wrist. 
These  tendons  lie  upon  the  same  plane,  and  pass  beneath  the 
annular  ligament,  under  those  of  the  superficial  flexor,  into  the 
palm,  where  they  diverge  to  pass  to  their  respective  fingers.  On 
the  first  phalanx  of  the  fingers  the  tendons  of  the  deep  flexor 
perforate  those  of  the  superficial,  and  are  inserted  into  the  bases 
of  the  third  or  ungual  phalanges.  It  derives  its  nerves  from  the 
interosseous  branch  of  the  median  and  from  the  ulnar  (Fig.  131, 
P-  337)-  Its  action  is  to  flex  the  third  or  ungual  phalanges,  the 
obliquity  of  its  insertion  giving  rapidity  and  extent  of  motion, 
flexion  continuing,  the  entire  hand  drawn  upon  the  forearm. 

Flexor  Longus  Pollicis.  —  This  muscle  is  situated  on  the 
front  surface  of  the  radius,  outside  the  preceding.  It  arises 
from  the  front  surface  of  the  radius,  between  the  tubercle  and 
the  oblique  ridge  above,  and  the  pronator  quadratus  below,  and 
from  the  interosseous  membrane.*  Its  tendon,  which  begins 
on  the  ulnar  side  of  the  muscle,  proceeds  beneath  the  annular 
ligament  to  the  base  of  the  last  phalanx  of  the  thumb.  Its 
nerve  comes  from  the  interosseous  branch  of  the  median  (Fig. 
I3i>  P-  337)-  Its  action  to  flex  the  third  or  ungual  phalanx  of  the 
thumb  which  from  the  bony  formation  allows  a  certain  adduc- 
tion to  be  accomplished  at  the  same  time. 

Pronator  Quadratus.  —  This  square  muscle  arises  from 
the   lower  fourth  of   the   ulna  and  from  a  strong  aponeurosis 

*  Sometimes  by  a  slip  from  the  coronoid  process. 


354 


DEEP  MUSCLES  OF  THE  FOREARM. 


which  covers  its  anterior   surface  ;  its  fibres  pass,  some  trans- 
versely, some  obhquely  outwards,  and  are  inserted  into  the  lower 


1.  Internal  head  of  triceps. 

2.  2.   Origin  of  the  pronator 

radii  teres. 

3.  Attachment  of  superficial 

flexors. 
3'  Tendon  of  the  biceps. 
3"  Tendon   of    the   brachial 

amicus. 

4.  4.    Flexor  carpi  ulnaris. 

5.  Supinator  longus  or  bra- 

chio-radialis. 

6.  Its  insertion. 

7     Supinator  brevis. 
7'.  Extensor    carpi    radialis 
longior. 

8,  8.   Tendon  of  the  exten- 

sor o  s  s  i  s  metacarpi 
pollicis,  excised  to 
show  the  insertion  of 
the  supinator  longus. 

9.  Flexor    profundus     digi- 

torum. 

10.  Its  four  tendons. 

11.  Tendon  to  the  index  fin- 

ger. 


12.  Tendon  to  the  middle 
finger,  which  has  been 
partly  excised  to  allow 
the  groove  to  be  seen 
and  which  holds  the 
tendon  of  the  flexor 
sublimis  digitorum. 

Tendon  of  the  flexor  sub- 
limis digitorum  of  the 
ring  finger,  cut  and 
turned  down  to  show 
the  groove  on  its  pos- 
terior surface. 

Tendon  of  the  profundus 
digitorum  to  the  little 
finger. 

15.  Lumbricales. 

16.  Attachment  of  the 
abductor  pollicis. 

Opponens  pollicis. 
Flexor  brevis  pollicis. 
Adductor  pollicis. 
Flexor  longus  pollicis. 
Tendon  of  this  muscle. 
22.   Attachments    of   the 

flexor    brevis     minimi 

digiti. 
Opponens  minimi  digiti. 


Fig.  136.  —  Drep  Flexoks  of  the  Fingers  and  Thumb. 

fourth  of  the  anterior  surface  and  the  outer  border  of  the  radius. 
\\. protiatcs  the  radius  on  the  ulna.  Its  neive  proceeds  from  the 
interosseous  branch  of  the  median. 


DISSECTION    OK    THE    PALM    OF    THE    HAND.  355 

Anterior  Interosseous  Artery.  —  Nearly  on  a  level  with 
the  insertion  of  the  biceps  the  ulnar  artery  gives  off  from  its 
outer  side  the  common  interosseous,  which  runs  backwards  for 
about  an  inch  (2.5  cm.),  and  divides  into  the  anterior  and/6'i-- 
terior  iuterosseous. 

The  anterior  interosseous  artery  runs  down  on  the  interosseous  membrane,  lying 
deeply  between  the  flexor  profundus  digitorum  and  flexor  longus  pollicis.  At  the 
upper  edge  of  the  pronator  quadralus  it  divides  into  two  branches,  one  of  which, 
the  smaller,  passes  beneath  the  muscle,  supplies  it  and  the  front  of  the  carpal  bones, 
communicating  with  the  anterior  carpal  arteries  from  the  radial  and  ulnar ;  the 
other,  the  more  important,  perforates  the  interosseous  membrane  and  helps  to 
supply  the  muscles  on  the  back  of  the  forearm. 

A  branch,  the  arteria  conies  nervi  mediant,  proceeds  from  the  anterior  interos- 
seous. It  lies  in  close  contact  with  the  nerve,  sometimes  in  its  very  centre ;  though 
usually  of  small  size,  it  may  be  as  large  as  the  ulnar  artery  itself,  and,  in  such 
cases,  it  passes  under  the  annular  ligament  with  the  nerve  to  join  the  palmar  arch. 
This  is  interesting,  because  it  helps  to  explain  the  recurrence  of  hemorrhage  from 
a  wound  in  the  palm,  even  after  the  radial  and  ulnar  arteries  have  been  tied. 

The  anterior  interosseous  artery  gives  off  branches  to  the  muscles  on  each  side ; 
also  the  nutrient  arteries  which  enter  the  radius  and  ulna,  near  the  centre  of  the 
forearm,  to  supply  the  medullary  membrane;  these  arteries  pass  upwards  towards 
the  elbow. 

Anterior  Interosseous  Nerve.  —  This  nerve  is  a  branch  of 
the  median  ;  it  generally  runs  close  to  the  radial  side  of  the 
artery,  and  supplies  the  flexor  longus  pollicis,  half  the  flexor 
profundus  digitorum,  and  the  pronator  quadratus  (Fig.  131, 
P-  337)- 

DISSECTION    OF   THE   PALM    OF   THE    HAND. 

Surface  Marking,  —  On  the  ulnar  side  of  the  palm  of  the 
hand  is  a  round,  long  eminence,  hypothenar,  which  corresponds 
with  the  muscles  of  the  ball  of  the  little  finger  ;  and  on  the 
radial  side,  placed  obliquely  over  the  metacarpal  bone  of  the 
thumb,  is  another  eminence,  thenar,  which  is  caused  by  the 
muscles  of  the  ball  of  the  thumb.  Between  the  two  eminences, 
at  the  wrist,  is  a  slight  depression,  corresponding  with  the  mid- 
dle of  the  annular  ligament,  and  which  broadens  out  towards  the 
fingers.  The  palm  of  the  hand,  about  an  inch  {2.^  cm.)  from 
the  clgfts  of  the  fingers,  presents  a  transverse  furrow,  which 
corresponds  with  the  metacarpo-phalangeal  articulations,  with 
the  distal  limit  of  the  synovial  sheaths  of  the  fle.xor  tendons, 
with  the  divisions  of  the  palmar  fascia  into  its  four  processes, 
and  with  the  transverse  metacarpal  ligament.  The  superficial 
palmar  arch  may  be  indicated  by  a  line  drawn  from  the  cleft  of 


356  PALMAR    FASCIA. 

the  extended  thumb  across  the  palm  ;  the  deep  palmar  arch  lies 
half  an  inch  {I J  mm.)  nearer  the  annular  ligament. 

Dissection.  —  Make  a  vertical  incision  along  the  centre  of 
the  palm,  and  a  transverse  one  along  the  bases  of  the  finger ; 
from  this  transverse  cut  continue  vertical  incisions  along  the 
front  of  the  fingers,  and  reflect  the  skin  ;  taking  care  not  to 
remove  a  small  cutaneous  muscle  —  the  palmaris  brevis  —  situ- 
ated over  the  ball  of  the  little  finger,  and  also  two  small  cutane- 
ous branches  of  the  median  and  ulnar  nerves,  which  are  found 
in  the  fat  of  the  palm. 

Observe  how  closely,  in  the  centre  of  the  palm,  the  skin  ad- 
heres to  the  palmar  fascia  beneath  it.  On  the  ball  of  the  little 
finger  and  the  distal  ends  of  the  metacarpal  bones  the  subcu- 
taneous structure  is  composed  of  a  dense  filamentous  tissue, 
which  contains  numerous  pellets  of  fat,  forming  an  elastic  pad. 
A  similar  padding  protects  the  palmar  surfaces  of  the  fingers. 
These  cushions  on  the  ends  of  the  fingers  defend  them  in  the 
powerful  actions  of  the  hand ;  they  are  also  useful  in  subservi- 
ence to  the  nerves  of  touch. 

The  palm  is  supplied  with  nerves  by  three  small  branches  — 
the  palmar  brancJi  of  the  median  passes  in  front  of  the  anterior 
annular  ligament  to  the  centre  of  the  palm  ;  Xh^  palmar  branch 
of  the  ulnar  supplies  the  inner  aspect  of  the  hand  ;  and  the 
anterior  branch  of  the  musculo-cutaneous  nerve  is  distributed  to 
the  skin  over  the  thenar  eminence.  The  terminal  branches  of 
these  cutaneous  nerves  communicate  with  each  other. 

Palmaris  Brevis. — This  small  cutaneous  muscle  is  situated 
on  the  inner  side  of  the  palm.  It  arises  from  the  inner  edge  of 
the  central  palmar  fascia,  and  the  annular  ligament,  and  is  in- 
serted into  the  skin  on  the  ulnar  border  of  the  palm.  Its  nse 
is  to  support  the  pad  on  the  inner  edge  of  the  palm  ;  it  acts 
powerfully  as  we  grasp ;  it  raises  the  inner  edge  of  the  palm, 
and  deepens  the  hollow  of  it,  forming  the  so-called  "cup  of 
Diogenes."      It  is  supplied  by  the  ulnar  7ierve. 

Palmar  Fascia.  —  This  fascia  has  a  silvery  lustre,  and  in  the 
centre  of  the  palm  is  remarkably  dense  and  strong.  It  is  di- 
vided into  three  portions  :  a  central,  by  far  the  stronge«t ;  an 
external,  covering  the  muscles  of  the  thumb  ;  and  an  internal, 
covering  the  muscles  of  the  little  finger.  From  the  deep  surface 
of  the  fascia  two  septa  dip  down  and  divide  the  palm  into  three 
separate  compartments  ;  one  for  the  ball  of  the  thumb,  a  second 
for  that  of  the  little  finger,  and  a  third  for  the  centre  of  the  palm. 


SUPERFICIAL    PALMAR    ARCH.  357 

The  fascia  is  formed  by  a  prolongation  from  the  anterior  an- 
nular ligament.  It  is  also  strengthened  by  the  expanded  ten- 
don of  the  palmaris  longus. 

The  central  portion  of  the  fascia  is  triangular,  with  the  apex 
at  the  wrist.  About  the  middle  of  the  palm  it  splits  into  four 
portions,  which  are  connected  by  transverse  tendinous  fibres, 
extending  completely  across  the  palm  and  corresponding  pretty 
nearly  to  the  transverse  furrow  of  skin  in  this  situation. 

Examine  any  one  of  these  four  portions  of  the  fascia,  and  you 
will  find  that  it  splits  into  two  strips  which  embrace  the  corre- 
sponding flexor  tendons,  and  are  intimately  connected  with  the 
transverse  metacarpal  ligament.  The  effect  of  this  is  that  the 
flexor  tendons  of  each  finger  are  kept  in  place  in  the  palm  by  a 
fibrous  ring.  Between  the  four  divisions  of  the  palmar  fascia 
the  digital  vessels  and  nerves  emerge,  and  descend  in  a  line  with 
the  clefts  between  the  fingers. 

In  the  hands  of  mechanics,  in  whom  the  palmar  fascia  is 
usually  very  strong,  we  find  that  slips  of  it  are  lost  in  the  skin 
at  the  lower  part  of  the  palm,  and  also  for  a  short  distance  along 
the  sides  of  the  fingers. 

The  chief  use  of  the  palmar  fascia  is  to  protect  the  vessels 
and  nerves  from  pressure  when  anything  is  grasped  in  the  hand. 
It  also  confines  the  flexor  tendons  in  their  proper  place. 

Beneath  the  interdigital  folds  of  the  skin  there  are  aponeurotic 
fibres  to  strengthen  them,  constituting  what  are  called  the  trans- 
verse ligaments  of  the  fingers.  They  form  a  continuous  liga- 
ment across  the  lower  part  of  the  palm,  in  front  of  the  digital 
vessels  and  nerves. 

Dissection.  —  Cut  through  the  palmar  fascia  at  its  attach- 
ment to  the  anterior  annular  ligament,  and  reflect  it  towards 
the  fingers,  so  as  to  expose  the  vessels,  nerves,  and  tendons  in 
the  palm.  The  vessels  lie  above  the  nerves,  and  the  tendons 
still  deeper.  There  is  an  abundance  of  loose  connective  tissue 
to  allow  the  free  play  of  the  tendons.  When  suppuration  takes 
place  in  the  palm  it  is  seated  in  this  tissue.  Reflect  for  a  mo- 
ment what  mischief  is  likely  to  ensue.  The  pus  cannot  come 
to  the  surface  through  the  dense  palmar  fascia  or  on  the  back 
of  tHe  hand ;  it  will,  therefore,  run  up  into  the  carpal  bursa 
under  the  annular  ligament,  and  make  its  way  deep  amongst 
the  tendons  of  the  forearm. 

Superficial  Palmar  Arch.  —  The  ulnar  artery,  having  passed 
over  the  annular  ligament,  near  the  pisiform  bone,  describes  a 


358 


SUPERFICIAL    PALMAR    ARCH. 


curve  across  the  upper  part  of  the  palm,  beneath  the  palmar 
fascia,  towards  the  thumb,  and,  gradually  diminishing  in  size, 
inosculates  with  the  superficialis  vol 35,  and  very  commonly  w^ith 
a  branch  from  the  arteria  radialis  indicis,  to  form  the  stiperficial 
palmar  arcJi.  The  curve  of  the  arch  is  directed  towards  the 
fingers,  its  greatest  convexity  descending  as  low  as  a  horizontal 


Radial  artery. 


Ulnar  artery. 


Ulnaris  profunda. 


Arteria  magna 

poUicis. 

Radialis  indicis. 


Fig.  137.  —  Diagram  op  the  Superficial  and  Deep  Palmar  Arches. 
1,2,3,4.    Interosseous  branches. 

line  drawn  across  the  junction  of  the  upper  with  the  middle 
third  of  the  palm. 

In  its  passage  over  the  annular  ligament  the  artery  lies  in  the 
furrow,  between  the  pisiform  and  unciform  bones,  and  is  pro- 
tected by  an  expansion  from  the  tendon  of  the  flexor  carpi 
ulnaris  to  the  palmaris  longus.     The   ulnar  nerve  lies  close  to 


ULNAR  NERVE  IN  THE  PALM.  359 

the  inner  side  of  the  artery,  both  being  covered  by  the  palmaris 
brevis.  In  the  pahii  the  artery  rests  for  a  short  distance  upon 
the  muscles  of  the  Httle  finger,  then  it  hes  upon  the  superficial 
flexor  tendons  and  the  divisions  of  the  ulnar  and  median  nerves, 
and  is  covered  by  the  palmar  fascia. 

Immediately  below  the  pisiform  bone  the  ulnar  artery  gives 
off  the  tihiaris  profunda,  which  sinks  deeply  into  the  palm,  be- 
tween the  origins  of  the  abductor  and  flexor  brevis  minimi  digiti, 
to  form  the  deep  palmar  arch,  by  joining  the  terminal  branch  of 
the  radial  artery.  It  is  accompanied  by  the  deep  branch  of  the 
ulnar  nerve. 

P'rom  the  concavity  of  the  arch  small  recurrent  branches  ascend  to  the  carpus, 
and  inosculate  with  the  other  carpal  branches  of  the  radial  and  ulnar  arteries. 

Four  digital  arteries  arise  from  the  convexity  of  the  superficial  palmar  arch. 
They  supply  all  the  digits,  except  the  thumb  and  the  radial  side  of  the  index 
finger.  T\\q  Jirst  descends  over  the  muscles  on  the  inner  side  of  the  palm,  to  the 
ulnar  side  of  the  little  finger,  along  which  it  runs  to  the  apex.  The  second,  third, 
2^nd  fourth  descend  nearly  vertically  between  the  tendons,  in  a  line  with  the  clefts 
between  the  fingers,  and,  about  half  an  inch  (ij  mm.)  above  the  clefts,  each  divides 
into  two  branches,  which  proceed  along  the  opposite  sides  of  the  fingers  nearly  to 
the  end  of  the  last  phalanges,  where  they  unite  to  form  an  arch  with  the  convexity 
towards  the  end  of  the  finger ;  from  this  arch  numerous  branches  supply  the 
papillae  at  the  tip  of  the  finger. 

In  the  palm  of  the  hand  the  digital  arteries,  before  they 
divide,  are  joined  by  branches  from  the  corresponding  palmar 
interosseous  arteries  (branches  of  the  deep  palmar  arch)  (Fig. 

137,  P-  358). 
The  digital  arteries  freely  communicate,  on  the  palmar  and 
dorsal  aspect  of  the  fingers,  by  transverse  branches,  which  sup- 
ply the  joints  and  the  sheaths  of  the  tendons.  Near  the  ungual 
phalanx,  a  considerable  branch  passes  to  the  back  of  the  finger, 
and  forms  a  network  of  vessels  which  supply  the  matrix  of  the 
nail. 

Ulnar  Nerve  in  the  Palm. — The.  ulnar  nerve  ^2i?,sts  over 
the  annular  ligament  into  the  palm,  on  the  inner  side  of  the 
ulnar  artery,  and  a  little  behind  it.  It  lies  in  the  groove  be- 
tween the  pisiform  and  unciform  bones,  so  that  it  is  perfectly 
secure  from  pressure.  Immediately  below  the  pisiform  bone, 
the  nerve  divides  into  a  superficial  and  a  deep  palmar  branch. 
The  deep  branch  supplies  the  muscles  forming  the  ball  of  the 
little  finger,  and  accompanies  the  ulnaris  profunda  artery  into 
the  palm,  to  supply  all  the  interosseous  muscles,  the  two  ulnar 
lumbricales,  and  it  ends  in  branches  which  are  distributed  to 
the  first  dorsal  interosseous,  the  adductor  pollicis,  and  the  inner 


360  MUSCLES    OF    THE    BALL    OF    THE    THUMB. 

head  of  the  flexor  brevis  polHcis  ;  it,  moreover,  sends  filaments 
which  ascend  to  supply  the  wrist-joint,  and  others  which  descend 
to  the  metacarpo-phalangeal  joints.  The  superficial  branch 
sends  tilaments  to  the  palmaris  brevis,  to  the  skin  on  the  inner 
side  of  the  palm,  and  then  divides  into  two  digital  nerves,  one 
for  the  supply  of  the  ulnar  side  of  the  little  finger,  the  other  for 
the  contiguous  sides  of  the  little  and  ring  fingers.*  This  branch 
also  communicates  with  the  median  nerve  behind  the  superficial 
palmar  arch.  All  the  digital  branches  run  along  the  sides  of 
the  fingers  to  their  extremities  superficial  to  their  corresponding 
arteries  (Fig.  131,  P-  337)- 

Anterior  Annular  Ligament  of  the  Carpus. f — This  ex- 
ceedingly strong  and  thick  ligament  confines  the  flexor  tendons 
of  the  fingers  and  thumb,  and  fastens  together  the  bones  of  the 
carpus.  It  is  attached,  externally,  to  the  tuberosity  of  the 
scaphoid  and  the  ridge  on  the  trapezium  ;  internally,  to  the  pisi- 
form and  unciform.  Its  upper  border  is  continuous  with  the 
aponeurosis  in  front  of  the  wrist ;  its  lower  is  connected  with 
the  palmar  fascia ;  its  anterior  surface  receives  the  expanded 
tendon  of  the  palmaris  longus,  and  gives  origin  to  most  of  the 
muscles  of  the  ball  of  the  thumb  and  little  finger  (Fig.  133,  p. 

344)- 

Now  proceed  to  the  muscles  composing  the  ball  of  the  thumb 
and  the  little  finger.  The  dissection  of  them  requires  consider- 
able care. 

Muscles  of  the  Ball  of  the  Thumb  or  Thenar  Eminence. 
—  The  great  strength  of  the  muscles  of  the  ball  of  the  thumb 
is  one  of  the  distinguishing  features  of  the  human  hand.  This 
strength  is  necessary  in  order  to  oppose  that  of  all  the  fingers. 
In  addition  to  its  strength,  the  thumb  enjoys  perfect  mobility. 
It  has  no  less  than  eight  muscles  —  namely,  an  abductor,  an 
opponens,  two  flexors,  three  extensors,  and  an  adductor. 

Abductor  Pollicis.  —  This  is  the  most  superficial  (Fig.  133, 
No.  24,  p.  344).  It  is  a  thin,  flat  muscle,  and  arises  from  the 
ridge  of  the  os  trapezium  and  the  annular  ligament.  It  passes 
forwards  and  outwards,  and  is  inserted  by  a  flat  tendon  into 
the  radial  side  of  the  base  of  the  first  phalanx  and  the  extensor 

*  Occasionally  a  branch  may  be  found  supplying  the  ulnar  .side  of  the  middle 
finger.  —  A.  H. 

t  Should  be  called  the  vetttral  annidar  fascia  or  vciilral  volar  lii^anu'/it,  and 
according  to  Dr.  J.  Francis  Walsh's  Boylston  I'rize  Kssay,  nSyj,  the  slieath  of  the 
tendon  of  the  flexor  carpi  radialis  is  attached  (o  it.  —  A.  II. 


MUSCLES    OF    THE    BALL    OF    THE    LITTLE    FINGER.  361 

aponeurosis  of  the  thumb.  Its  action  is  to  abduct  and  flex  the 
first  phalanx  of  the  thumb.  Its  nerve  comes  from  the  median. 
Reflect  it  from  its  insertion  to  expose  the  following  :  — 

Opponens  Pollicis. — This  muscle  arises  from  the  front  of 
the  OS  trapezium  (Fig.  136,  No.  17,  p.  354)  beneath  the  abduc- 
tor, and  from  the  annular  ligament,  and,  passing  forwards  and 
outwards,  is  inserted,  more  or  less  obliquely,  into  the  whole 
length  of  the  radial  side  of  the  metacarpal  bone  of  the  thumb. 
The  action  of  this  powerful  muscle  is  to  rotate  the  metacarpal 
bone  on  its  vertical  axis,  and  then  draw  the  whole  thumb  in- 
wards, thus  opposing  the  thumb  to  all  the  fingers.  Its  nerve 
comes  from  the  median.  Reflect  it  from  its  insertion,  to  expose 
the  following :  — 

Flexor  Brevis  Pollicis.  — This  muscle  has  two  origins,  be- 
tween which  runs  the  tendon  of  the  flexor  longus  pollicis :  one, 
the  superficial,  from  the  annular  ligament  and  trapezium  ;  the 
otJicr,  the  deep,  from  the  trapezium,  trapezoid,  os  magnum,  the 
bases  of  the  second  and  third  metacarpal  bones,  and  the  sheath 
of  the  tendon  of  the  flexor  carpi  radialis.  It  is  inserted  by  two 
strong  tendons  into  the  base  of  the  first  phalanx  of  the  thumb 
on  the  inner  and  outer  sides ;  the  superficial  tendon  being 
connected  with  the  abductor  pollicis,  and  the  deep  one  with  the 
adductor  pollicis.  A  sesamoid  bone  is  found  in  each  of  the 
tendons.  The  tendons  of  insertion  of  this  muscle  are  separated 
by  the  long  flexor  tendon  of  the  thumb  and  the  arteria  magna 
pollicis.  Its  action  is  to  bend  the  first  phalanx  of  the  thumb. 
The  individual  bellies  acting  to  assist  in  abduction  and  adduc- 
tion. The  superficial  portion  is  supplied  by  the  median  nerve ; 
the  deep,  by  the  ulnar  (Fig.  136,  No.  18,  p.  354). 

Adductor  Pollicis. — This  triangular  x^w^aXo.  arises  from  the 
palmar  aspect  of  the  shaft  of  the  metacarpal  bone  of  the  middle 
finger ;  its  fibres  converge  and  are  inserted,  along  with  the  deep 
or  inner  portion  of  the  flexor  brevis  pollicis,  into  the  base  of  the 
first  phalanx  of  the  thumb  and  the  internal  sesamoid  bone.  Its 
action  is  to  draw  the  thumb  towards  the  palm,  as  when  we  bring 
the  tips  of  the  thumb  and  little  finger  into  contact.  It  is  sup- 
plied by  the  deep  branch  of  the  ulnar  nerve,  which  also  supplies 
the  deep  head  of  the  flexor  brevis  pollicis.  The  other  muscles 
of  the  ball  of  the  thumb  are  supplied  by  the  median  nerve  (Fig. 
136,  No.  19,  p.  354). 

Muscles  of  the  Ball  of  the  Little  Finger  or  Hypothenar 
Eminence.  —  The  muscles   of  the  little  finger  correspond  in 


362  MUSCLES    OF    THE    BALL    OF    THE    LITTLE    FINGER. 

some  measure  with  those  of  the  thumb.  Thus  there  is  an  ab- 
ductor, a  flexor  brevis,  and  an  opponens  minimi  digiti.  All 
derive  their  nerves  from  the  deep  branch  of  the  ulnar. 

Abductor  Minimi  Digiti. —  This,  the  most  superficial  of 
the  muscles  of  the  little  finger,  arises  (Fig.  134,  No.  23,  p. 346) 
from  the  pisiform  bone,  and  from  the  tendinous  expansion  of  the 
flexor  carpi  ulnaris  ;  it  is  inserted  by  a  flat  tendon  into  the  inner 
side  of  the  base  of  the  first  phalanx  of  the  little  finger,  and  is 
prolonged  according  to  Walsh*  as  an  interphalangeal  muscle  to 
be  lost  in  the  tendon  common  to  it  and  the  common  extensor 
tendon,  and  is  inserted  into  the  bases  of  the  second  and  third 
phalanges,  posteriorly.  Its  actiojt  is  to  extend  the  third  on  the 
second  and  the  second  on  the  first  phalanges,  and  then  abduct 
the  whole  fipger.  It  may  flex  the  phalanges  and  then  abduct. 
Its  nej've  comes  from  the  deep  branch  of  the  ulnar. 

Flexor  Brevis  Minimi  Digiti.  —  It  arises  irom.  the  apex  of 
the  unciform  bone  and  annular  ligament,  and  is  inserted  with 
the  tendon  of  the  abductor  into  the  base  of  the  first  phalanx 
and  to  the  flexor  sheath  of  the  little  finger.  Its  action  is  simi- 
lar to  that  of  the  abductor.  Nerve  from  deep  branch  of  ulnar. 
Between  the  origins  of  the  abductor  and  flexor  brevis  minimi 
digiti,  the  deep  branch  of  the  ulnar  artery  and  nerve  sinks  down 
to  form  the  deep  palmar  arch  (Fig.  134,  No.  24,  p.  346). 

Opponens  Minimi  Digiti.  —  The  last  two  muscles  must  be 
reflected  from  their  insertion,  to  expose  the  opponens  minimi 
digiti.  It  arises  from  the  unciform  process  and  the  annular 
ligament,  and  is  inserted  along  the  ulnar  side  of  the  shaft  of  the 
metacarpal  bone  of  the  little  finger.  Its  action  is  to  flex  the 
little  finger,  and  rotates  on  its  long  axis,  thus  assisting  to  pro- 
duce the  cupping  or  depression  of  the  palm.  Thus  it  greatly 
strengthens  the  grasp  of  the  palm.  Nerve  from  deep  branch 
of  ulnar  (Fig.  136,  No.  23,  p.  354). 

Dissection.  -^  Cut  vertically  through  the  anterior  annular 
ligament,  and  observe  that,  with  the  carpal  bones,  it  forms  an 
elliptical  canal,  with  the  broad  diameter  transversely.  This 
canal  is  lined  by  a  synovial  membrane  which  is  reflected  loosely 
over  the  tendons.  Superficial  to  the  ligament  pass  the  palmaris 
longus,  the  ulnar  artery  and  nerve,  the  fibrous  expansion  from 
the  flexor  carpi  ulnaris  covering  these  vessels  and  nerve,  and 
the  palmar  branch  of  the  median  and  ulnar  nerves  ;  beneath  it 
pass  the  superficial  and  deep  flexor  tendons  of  the  fingers,  the 
*  Boylston  Prize  E.ssay.     Dr.  J.  Francis  Walsh,  1897. 


MEDIAN  NERVE  IN  THE  PALM.  363 

long  flexor  tendon  of  the  thumb,  and  the  median  nerve.  The 
tendon  of  the  flexor  carpi  radialis  does  not  run  with  the  other 
tendons,  but  is  contained  in  a  distinct  sheath,  lined  by  a  sepa- 
rate synovial  membrane,  formed,  partly  by  the  annular  ligament, 
and  partly  by  the  groove  in  the  trapezium. 

Median  Nerve  in  the  Palm.  —  In  its  passage  under  the 
annular  ligament,  the  median  nerve  is  enveloped  in  a  fold  of 
synovial  membrane,  and  lies  upon  the  flexor  tendons.  Here  it 
becomes  enlarged  and  flattened,  and  of  a  pinkish  color,  and 
divides  into  two  nearly  equal  parts  :  the  external  gives  a  recur- 
rent branch  to  the  muscles  of  the  ball  of  the  thumb  —  namely, 
to  the  abductor  pollicis,  the  opponens  pollicis,  and  the  outer 
head  of  the  flexor  brevis  pollicis,  and  then  terminates  in  three 
digital  nerves,  two  of  which  are  distributed  to  the  thumb,  and 
the  third  to  the  radial  side  of  the  index  finger  ;  the  mtcrnal 
gives  digital  branches  which  supply  the  ulnar  side  of  the  index, 
both  sides  of  the  middle  finger,  and  the  radial  side  of  the  ring 
finger  (Fig.   131,  p.  337). 

The  tivo  nerves  to  the  thumb  proceed,  one  on  each  side  of  the  long  flexor 
tendon,  to  the  last  phalanx:  the  outer  one  being  connected  with  a  terminal  fila- 
ment of  the  radial. 

The  third  digital  nerve  runs  along  the  radial  side  of  the  index  finger.  The 
fourth  descends  towards  the  cleft  between  the  index  and  middle  fingers,  and  sub- 
divides into  two  branches,  which  supply  their  opposite  sides.  The  fifth  is  joined 
by  a  filament  from  one  of  the  ulnar  digital  nerves,  and  then  subdivides  above  the 
cleft  between  the  middle  and  ring  fingers,  to  supply  their  opposite  sides. 

Two  small  branches  are  given  off  from  the  third  and  fourth  digital  nerves  to 
supply  the  two  radial  lumbricales,  the  two  ulnar  being  supplied  by  the  vdnar  nerve. 

About  an  inch  and  a  quarter(j>.7  cm.)  above  the  clefts  between  the  fingers,  each 
digital  nerve  subdivides  into  two  branches,  between  which  the  digital  artery  passes 
and  bifurcates  lower  down ;  therefore  a  vertical  incision  down  the  cleft  would 
divide  the  artery  before  the  nerve. 

In  their  course  along  the  fingers  and  thumb,  the  nerves  lie 
superficial  to  the  arteries,  and  nearer  to  the  flexor  tendons. 
About  the  base  of  the  first  phalanx  each  nerve  sends  a  dorsal 
branch,  which  runs  along  the  back  of  the  finger  nearly  to  the 
extremity,  communicating  with  the  dorsal  branches  derived 
from  the  radial  and  ulnar  nerves.  Near  the  ungual  phalanx 
another  dorsal  or  ungual  branch  is  distributed  to  the  skin  around 
and  beneath  the  matrix  of  the  nail.  Each  digital  nerve  termi- 
nates in  the  cushion  at  the  end  of  the  finger  in  a  brush  of  fila- 
ments, with  their  points  directed  into  the  papillae  of  the  skin. 

Flexor  Tendons  and  their  Sheaths.  —  Immediately  below 
the   annular  ligament  the  tendons   separate  from  each  other: 


364  FLEXOR    TENDONS    AND    THEIR    SHEATHS. 

near  the  metacarpal  joints  they  pass  in  pairs,  through  strong 
fibrous  rings  (p.  356)  formed  by  the  divisions  of  the  palmar 
fascia.  Below  the  metacarpal  joint  the  two  tendons  for  each 
finger  enter  the  sheath,  tJieca,  which  confines  them  in  their 
course  along  the  phalanges.  It  is  formed  by  a  strong  fibrous 
membrane,  which  is  attached  to  the  ridges  on  the  phalanges, 
and  converts  the  groove  in  front  of  these  bones  into  a  complete 
canal,  exactly  large  enough  to  contain  the  tendons.  The  density 
of  the  sheath  varies  in  particular  situations,  otherwise  there 
would  be  an  obstacle  to  the  easy  flexion  of  the  fingers.  To 
ascertain  this,  cut  open  one  of  the  sheaths  along  its  entire  length ; 
you  will  then  see  that  it  is  much  stronger  between  the  joints 
than  over  the  joints  themselves.  Through  these  sheaths  inflam- 
mation, commencing  in  the  integuments  of  the  finger,  may 
readily  extend  to  the  synovial  membrane  of  the  tendon. 

In  cases  of  whitlow,  when  pus  forms  in  the  theca,  the  incision 
should  be  made  deep  enough  to  lay  open  this  fibro-osseous  canal, 
without  which  the  incision  will  be  of  no  use.  It  is  obvious  that 
the  incision  should  be  made  down  the  centre  of  the  finger,  to 
avoid  the  digital  nerves  and  arteries.  If  this  opening  be  not 
timely  made,  the  flexor  tendons  are  likely  to  slough,  and  the 
finger  becomes  stiff.* 

But  what  protects  the  joints  of  the  fingers  where  the  flexor 
tendons  play  over  them  ?  Look  into  an  open  sheath  and  you 
will  see  that  in  front  of  the  joints  the  tendons  glide  over  a 
smooth  fibro-cartilaginous  structure  caled  the /«//«^r  ligament. 

To  facilitate  the  play  of  the  tendons  the  interior  of  the  sheath, 
as  well  as  the  tendons,  is  lined  by  a  synovial  membrane,  of  the 
extent  of  which  it  is  important  to  have  a  correct  knowledge. 
With  a  probe  you  may  ascertain  that  the  synovial  membrane  is 
reflected  from  the  sheath  upon  the  tendons,  a  little  above  the 
metacarpal  joints  of  the  fingers  —  that  is,  nearly  in  a  line  with 
the  transverse  fold  in  the  skin  in  the  lower  third  of  the  palm. 
Towards  the  distal  end  of  the  finger  the  synovial  sheath  stops 

*  On  closer  inspection  it  will  be  observed  that  the  sheath  is  composed  of 
bands  of  fibres,  which  take  different  directions,  and  have  received  distinct  names. 
The  strongest  are  called  the  lii^amcnta  vaginalia.  They  constitute  the  sheath  over 
the  body  of  the  phalanx,  and  extend  transversely  from  one  side  of  the  bone  to  the 
other.  Tha  lis^mtnettta  criuiata  are  two  slips,  which  cross  obliquely  over  the  ten- 
dons. The  lii^amenta  annularia  are  situated  immediately  in  front  of  the  joints, 
and  may  be  considered  as  thin  continuations  of  the  ligamenta  vaginalia  They 
consist  of  fibres,  which  are  attached  on  either  side  to  the  lateral  ligaments  of  the 
joints,  and  pass  transversely  over  the  tendons. 


BURSAL  SAC  OF  THE  CARPUS.  365 

short  of  the  last  joint,  so  that  it  is  not  injured  in  amputation  of 
the  ungual  phalanx. 

And  now  notice  how  the  tendons  are  adapted  to  each  other 
in  their  course  along  the  finger.  The  superficial  flexor,  near  the 
root  of  the  finger,  becomes  slightly  grooved  to  receive  the  deep 
flexor ;  about  the  middle  of  the  first  phalanx  it  splits  into  two 
portions,  through  which  the  deep  flexor  passes.  The  two  por- 
tions reunite  below  the  deep  tendon  so  as  to  embrace  it,  and 
then  divide  a  second  time  into  two  slips,  which  interlace  with 
each  other,  and  are  inserted  into  the  sides  of  the  second  phalanx. 
The  deep  flexor,  having  passed  through  the  opening  of  the  super- 
ficial one,  is  inserted  into  the  base  of  the  last  phalanx  (Fig.  i  '^,6, 
Nos.  12,  13,  p.  354). 

In  what  way  are  the  tendons  supplied  with  blood.?  Raise  and 
separate  the  tendons,  and  you  will  see  that  slender  but  very 
vascular  folds  of  synovial  membrane  {vinciila  tendimini)  run  up 
from  the  phalanges  and  convey  blood-vessels  to  the  tendons. 

The  tendon  of  the  flexor  longiis  pollicis  lies  on  the  radial  side 
of  the  other  tendons  beneath  the  annular  ligament.  It  passes 
between  the  two  portions  of  the  flexor  brevis  pollicis  and  the 
two  sesamoid  bones  of  the  thumb,  enters  its  proper  sheath,  and 
is  inserted  into  the  base  of  the  last  phalanx.  Its  synovial  sheath 
is  prolonged  from  the  large  bursa  of  the  flexor  tendons  beneath 
the  annular  ligament,  and  accompanies  the  tendon  down  to  the 
last  joint  of  the  thumb ;  consequently  the  sheath  is  injured  in 
amputation  of  the  last  phalanx. 

Bursal  Sac  of  the  Carpus. — A  large  and  loose  synovial 
sac  (bursa  of  the  carpus)  facilitates  the  play  of  the  tendons  be- 
neath the  anterior  annular  ligament.  It  lines  the  under  surface 
of  the  ligament  and  the  groove  of  the  carpus,  and  is  reflected  in 
loose  folds  over  the  tendons.  It  is  prolonged  up  the  tendons 
for  an  inch  and  a  half  or  two  inches  (J.^*  to  ^  cm.),  and  forms  a 
cul-de-sac  above  the  ligament.  Below  the  ligament  the  bursa 
extends  into  the  palm,  and  sends  off  prolongations  for  each  of 
the  flexor  tendons,  which  accompany  them  down  to  the  middle  of 
the  hand.  You  will  understand  that  when  the  bursa  is  inflamed 
and  distended  by  fluid,  there  will  be  a  bulging  above  the  annular 
ligament  and  another  in  the  palm,  with  perceptible  fluctuation 
between  them,  the  unyielding  ligament  causing  a  constriction 
in  the  centre. 

Lumbricales. — These  four  slender  muscles,  one  for  each 
finger,  are  attached  to  the  deep  flexor  tendons  in   the  palm. 


T,66  RADIAL  ARTERY  IN  THE  PALM. 

All  of  them  arise  by  fleshy  fibres  from  the  radial  side  and 
palmar  surface  of  the  deep  tendon  of  their  corresponding  finger  ; 
the  third  and  fourth  also  arise  from  the  adjacent  sides  of  two 
tendons.  Each  terminates  in  a  broad,  thin  tendon,  which 
passes  over  the  radial  side  of  the  first  joint  of  the  finger  and  is 
inserted,  by  a  broad  expanded  aponeurosis,  into  the  extensor 
tendon  on  the  dorsal  aspect  of  the  first  phalanx  of  the  finger. 
Their  action  is  to  flex  the  first  phalanx  and  to  extend  the  second 
and  third  phalanges.  Being  inserted  near  the  centre  of  motion, 
they  can  move  the  fingers  with  great  rapidity.  As  they  pro- 
duce the  quick  motions  of  the  musician's  fingers,  they  were 
called   by  the   old  anatomists  fidicinales   (Fig.    136,    No.    15, 

P-  354). 

The  two  ulnar  lumbricales  are  supplied  by  the  deep  branch  of 
the  ulnar  nerve  ;  the  two  radial  by  the  third  and  fourth  digital 
branches  of  the  median  nerve. 

Dissection.  —  Now  cut  through  all  the  flexor  tendons,  and 
remove  the  deep  fascia  of  the  palm,  to  see  the  deep  arch  of 
arteries  and  its  branches.* 

Branches  of  the  Radial  Artery  in  the  Palm.  — The  radial 
artery,  sinking  into  the  space  between  the  first  and  second  met- 
acarpal bones,  and  between  the  two  heads  of  the  abductor  in- 
dicis,  enters  the  palm  between  the  inner  head  of  the  flexor 
brevis  and  the  adductor  pollicis,  and  gives  off  three  branches  — 
the  arteria  princeps  pollicis,  the  radialis  indicis,  and  the  palmaris 
profunda,  which  unites  with  the  deep  ulnar  artery  to  form  the 
deep  arch. 

The  arteria  princeps  pollicis  runs  behind  the  deep  head  of  the  flexor  brevis 
polhcis  and  in  front  of  the  abductor  indicis  (first  dorsal  interosseous),  close  along 
the  metacarpal  bone  of  the  thumb;  in  the  inlei-val  between  the  lower  portions  of 
the  flexor  brevis  ])ollicis,  the  artery  divides  into  two  cUgital  branches,  which  pro- 
ceed one  on  either  side  of  the  thumb,  and  inosculate  at  the  apex  of  the  last 
phalanx.  Their  distribution  and  mode  of  termination  are  like  those  of  the  other 
digital  arteries. 

The  arteria  radialis  indicis  runs  between  the  abductor  indicis  and  adductor 
pollicis,  along  the  radial  side  of  the  index  finger  to  the  end,  where  it  forms  an 
arch  with  the  other  digital  artery,  a  branch  of  the  ulnar.  Near  the  lower  margin 
of  the  abductor  pollicis,  the  radialis  indicis  generally  receives  a  branch  from  the 
princeps  pollicis,  and  gives  a  branch  to  the  superficial  palmar  arch. 

T\\Q.  palmaris  profunda  may  be  considered  as  the  continuation 
of  the  radial  artery.  It  enters  the  palm  between  the  inner 
head  of  the  flexor  brevis  and  the  adductor  pollicis,  and,  running 

*  The  course  and  relations  of  the  radial  artery  as  it  winds  round  the  wrist  will 
be  described  in  the  dissection  of  the  back  of  the  hand. 


MUSCLES    OF    THE    BACK.    CONNECTED    WITH    THE    AKM.      367 

upon  the  bases  of  the  metacarpal  bones,  inosculates  with  the 
deep  branch  of  the  ulnar  artery,  thus  completing  the  deep  pal- 
mar arch.  From  the  concavity  of  the  arch  small  recurrent 
branches  ascend  to  supply  the  bones  and  joints  of  the  carpus, 
inosculating  with  the  other  carpal  arteries. 

From  the  convexity  of  the  arch  three  or  four  small  branches,  called /<^/wr^r 
interosseous  (Fig.  137,  p.  358),  descend  to  supply  the  interosseous  muscles,  and 
near  the  clefts  of  the  fingers  communicate  with  the  digital  arteries.  These  pal- 
mar interosseous  branches  are  sometimes  of  considerable  size,  and  take  the  place 
of  one  or  more  of  the  digital  arteries,  ordinarily  derived  from  the  superficial  pal- 
mar arch.  Three  branches,  called  ^er/oratifio-,  pass  between  the  upper  ends  of  the 
metacarpal  bones  to  the  back  of  the  hand,  and  communicate  with  the  carpal 
branches  of  the  radial  and  ulnar. 

Deep  Branch  of  the  Ulnar  Nerve.  — This  nerve  sinks  into 
the  palm  with  the  ulnaris  profunda  artery,  between  the  abductor 
and  fle.xor  brevis  minimi  digiti.  It  then  runs  with  the  deep 
palmar  arch  towards  the  radial  side  of  the  palm,  and  terminates 
in  the  adductor  pollicis,  in  the  inner  or  deep  head  of  the  flexor 
brevis  polHcis,  and  in  the  first  dorsal  interosseous.  Between 
the  pisiform  and  unciform  bones,  the  nerve  gives  a  branch  to 
each  of  the  muscles  of  the  little  finger.  Subsequently  it  sends 
branches  to  each  interosseous  muscle  and  to  the  two  inner  lum- 
bricales  (Fig.  131,  No.  32,  p.  337). 

The  tendon  of  the  flexor  carpi  radialis  in  the  palm  must  now 
be  followed  to  its  insertion  into  the  base  of  the  second  metacar- 
pal bone. 

The  dissection  of  the  remaining  muscles  of  the  palm  called, 
from  their  position,  mterossei,  must  be,  for  the  present,  post- 
poned. 

MUSCLES  OF   THE   BACK    CONNECTED   WITH 
THE    ARM. 

Dissection.  —  Make  an  incision  down  the  middle  of  the  spine 
from  the  occiput  to  the  sacrum  ;  another,  from  the  last  thoracic 
vertebra  upwards  and  outwards  to  the  acromion  ;  and  a  third 
from  the  sacrum  along  the  crest  of  the  ilium  ;  then  reflect  the 
skin  outwards  from  the  dense  subcutaneous  tissue,  in  which  will 
be  found  the  following  cutaneous  nerves  :  — 

Cutaneous  Nerves  of  the  Back. — These  are  derived  from  the  posterior 
divisions  of  the  spinal  nerves,  and  correspond,  generally,  to  the  number  of  the 
vertebras.  The  posterior  primary  branches,  much  smaller  than  the  anterior,  divide, 
between  the  transverse  processes,  mio  external  2L.r\Ainternal\)xa.\\c\\%s,  with  the  ex- 
ception of  the  suboccipital,  the  fourth  and  fifth  sacral,  and  the  coccygeal  nerves. 


j6S  NERVES    OF    THE    BACK. 

Posterior  Branches  of  the  Cervical  Nerves.  —  The  postei-ior  primary 
branches  of  the  cervical  nerves  (except  the  first*)  divide  into  external  and  internal 
branches:  the  .fxArw^// are  distributed  solely  to  some  of  the  muscles  of  the  neck, 
and  which  will  be  dissected  later  on;  the  ititcnial,  larger  than  the  external,  are 
distributed  in  the  following  manner  :  the  second,  or  the  great  occipital  tierz'e,  per- 
foiates  the  complexus  and  ramifies  on  the  back  of  the  scalp  with  the  occipital 
artery;  the  third, fourth,  2i.ndffth  nerves,  after  sending  branches  to  themultifidus 
spina;,  semi-spmalis,  and  the  complexus,  emerge  through  the  trapezius  close  to 
the  spinous  processes,  and  then  pass  transversely  across  that  muscle  to  supply 
the  skin  over  it ;  the  branch  of  the  third  cervical  nei-ve  sometimes  sends  a  bianch 
to  the  back  of  the  scalp  ;t  the  branches  of  the  sixth,  sez'etith,  and  eighth  are  tmall, 
and  are  situated  beneath  the  semispinalis,  to  which  they  are  distributed. 

Posterior  Branches  of  the  Thoracic  Nerves. — The  external  branches  be- 
come superficial  between  the  longissimus  dorsi  and  the  ilio-costalis,  and  supply 
these  muscles  and  the  other  divisions  of  the  erector  spinae  ;  the  six  lower  supjiy 
cutaneous  nerves  in  the  hne  of  the  angles  of  the  ribs.  The  internal  branches,  as 
to  the  upper  six  thoracic,  emerge  between  the  multifidus  spinae  and  stmispinalis, 
and,  passing  horizontally  outwards,  end  in  branches  to  the  skin  close  to  the  spi- 
nous processes;  that  from  the  second  ramifies  over  the  spine  of  the  scapula;  the 
six  lower  do  not  become  cutaneous,  but  terminate  in  the  multifidus  spinae. 

Posterior  Branches  of  the  Lumbar  Nerves.  —  The  external  branches  from 
the  first,  second,  and  third  lumbar  ner\es  perforate  the  ilio-costalis  and  the  latissi- 
mus  dorsi,  and  then  descend  over  the  crest  of  the  ilium,  supplying  cutaneous 
branches  to  the  gluteal  region;  the  fourth  supplies  the  erector  spina  without  be- 
coming cutaneous ;  the  fifth  sends  down  a  branch  to  con  municate  with  the  fiist 
sacral  ner\'e.     The  intertial  branches  are  small,  and  end  in  the  multifidus  spinae. 

Posterior  Branches  of  the  Sacral  Nerves.  —  The  external  branches  of  the 
upper  three  sacral  nerves  form  a  series  of  loops  vAih.  themselves,  and  also  with 
the  last  lumbar  above  and  the  fourth  sacral  below;  they  pass  to  the  superficial 
surface  of  the  great  sacro-sciatic  hgament,  where  they  form  another  series  of  loops, 
from  which  filaments  are  distributed  to  the  skir  after  piercing  the  gluteus  maxi- 
mus.  The  internal  branches  of  the  three  upper  sacral  nerves  are  distributed  to 
the  multifidus  spina.  The  posterior  branches  of  the  fourth  and  fifth  sacral  nerves 
do  not  di\'ide  into  external  and  internal  branches,  but  form  a  loop,  the  lower  one 
being  joined  ^^■ith  the  coccygeal  nerve. 

Coccygeal  Nerve.  —  The  posterior  division  of  this  nerve,  after  being  joined 
by  a  branch  from  the  last  sacral,  is  distributed  to  the  posterior  aspect  of  the 
coccyx. 

Dissection.  — The  trapezius  and  latissimiis  dorsi,  which  form 
the  first  layer  of  muscles,  must  now  be  cleaned  by  putting  them 
on  the  stretch  and  reflecting  the  connective  tissue  which  covers 
them  ;  they  should  then  be  dissected  in  the  course  of  their 
fibres. 

Trapezius.  —  Alone,  this  muscle  is  triangular;  with  its  fel- 
low, it  presents  a  trapezoid  form.  It  arises  from  the  inner 
fourth,  more  or  less,  of  the  superior  curved  line  of  the  occiput, 

*  This  nerve  has  already  been  described  in  the  dissection  of  the  suboccipital 
triangle  (p.  292). 

t  The  internal  branches  of  the  first,  second,  and  third  cervical  nerves  form  a 
communication  beneath  the  complexus,  which  is  called  by  Crave\\h\&r  Xhc posterior 
cervical  plexus. 


CUTANEOS  NERVES  OF  THE  BACK. 


369 


a,ti.  Small  occipital  nerve 
trom  the  cervical  plex- 
us ;  I ,  external  muscu- 
lar branches  of  the  first 
cervical  nerve  and  un- 
ion by  a  loop  with  the 
second  ;  2,  the  rectus 
capitis  posticus  major, 
with  the  great  occipital 
nerve  passing  round  the 
short  muscles  and  pier- 
cing the  complexus;  the 
external  branch  is  seen 
to  the  outside  ;  2',  the 
great  occipital  ;  3,  ex- 
ternal branch  of  the 
posterior  primary  divi- 
sion of  the  third  nerve  ; 
3',  its  internal  branch,  f 
or  third  occipital  nerve  ; 
4',  5',  6',  7',  8',  internal 
branches  of  the  several 
corresponding  nerves 
on  the  left  side  ;  the  ex- 
ternal branches  of  these 
nerves  proceeding  to 
muscles  are  displayed 
on  the  right  side  :  li  i 
to  db,  and  thence  to  d 
12,  external  muscular 
branches  of  the  poste- 
rior primary  divisions 
of  the  twelve  thoracic 
nerves  on  the  right  side; 
d  i' ,  to  db' ,  the  internal 
cutaneous  branches  of 
the  six  upper  thoracic 
nerves  on  the  left  side  ; 
d  y'  \.o  d  12',  cutaneous 
branches  of  the  six 
lower  thoracic  nerves 
from  the  extern  a  1 
branches  ;  /,  /,  external 
branches  of  the  poster- 
ior primary  branches  of 
several  lumbar  nerves 
on  the  right  side  pier- 
cing the  muscles,  the 
lower  descending  over 
the  gluteal  region  ;  /', 
/',  the  same  more  super- 
ficially on  the  left  side  ; 
s,  s,  on  the  right  side, 
the  issue  and  union  by 
loops  of  the  posterior 
primary  divisions  of 
four  sacral  nerves  ,  s", 
s',  some  of  these  dis- 
tributed to  the  skin  on 
the  left  side. 


Fig.  138. —  Diagram  of  the  Cutaneous  Nerves  of  the  Rack. 


370  TRAPEZIUS. 

from  the  ligamentum  nuchre,*  from  the  spinous  processes  of 
the  seventh  cervical,  and  all  the  thoracic  vertebrae,  and  from 
their  supraspinous  ligament.  The  fibres  converge  towards  the 
shoulder.  The  upper  pass  downwards  and  outwards,  and  are 
inserted  by  fleshy  fibres  into  the  external  third  of  the  clavicle  ; 
the  middle  pass  transversely  outwards  into  the  inner  border 
of  the  acromion  and  the  superior  lip  of  the  spine  of  the  scapula ; 
the  lower  pass  upwards  and  outwards,  and  terminate  in  a  thin 
tendon,  which  plays  over  the  triangular  surface  at  the  back  of 
the  scapula,  and  is  inserted  into  the  beginning  of  the  spine. 
The  insertion  of  the  trapezius  exactly  corresponds  to  the  origin 
of  the  deltoid,  and  the  two  muscles  are  connected  by  a  thin 
aponeurosis  over  the  spine  and  acromion.  If  both  the  trapezius 
muscles  be  exposed,  observe  that,  between  the  sixth  cervical 
and  the  third  thoracic  vertebras,  their  origin  presents  an  aponeu- 
rotic space  of  an  elliptical  form  (Fig.  139,  p.  371). 

The  structures  covered  by  the  trapezius  are :  the  splenius, 
the  complexus,  the  levator  anguli  scapulas,  the  rhomboidei  minor 
and  major,  the  supraspinatus,  a  small  part  of  the  infraspinatus, 
the  serratus  posticus  superior,  the  vertebral  aponeurosis,  the 
latissimus  dorsi,  the  ilio-costalis,  the  spinal  accessory  nerve,  and 
the  superficialis  colli  artery. 

The  fixed  point  of  the  muscle  being  at  the  vertebral  column, 
all  its  fibres  tend  to  raise  the  shoulder.  The  deltoid  cannot 
raise  the  humerus  beyond  an  angle  of  ninety  degrees  :  beyond 
this,  the  elevation  of  the  arm  is  principally  effected  by  the  rota- 
tory movement  of  the  scapula.  The  trapezius  is  in  strong  action 
when  a  weight  is  borne  upon  the  shoulders  ;  again,  its  middle 
and  inferior  fibres  act  powerfully  in  drawing  the  scapula  back- 
wards, as  in  preparing  to  strike  a  blow.  If  both  muscles  act, 
they  draw  the  head  backwards  ;  if  one  only  acts,  it  draws  the 
head  to  the  same  side.  It  is  supplied  by  the  nervus  accessorius 
and  the  deep  branches  of  the  cervncal  plexus,  and  by  the  super- 
ficialis colli  artery. 

Latissimus  Dorsi. f  —  This  broad  flat  muscle  occupies  the 

*  The  ligamentum  nuchre  is,  in  man,  only  a  rudiment  of  the  great  elastic  liga- 
ment which  supports  the  weight  of  the  head  in  quadrupeds.  It  extends  from  the 
spine  of  the  occiput  to  the  spines  of  all  the  cervical  vertebrae,  except  the  atlas; 
otherwise  it  would  imj^ede  the  free  rotation  of  the  head.  In  the  giraffe  this  liga- 
ment is  six  feet  long  and  as  thick  as  a  man's  forearm.  Professor  Quekett  states 
that  when  divided  it  shrinks  at  least  two  feet. 

t  This  muscle  is  classified  by  Morris  as  forming  the  second  layer  with  the 
levator  anguli  scapuji,  the  rhomboidei.     (A.  H.) 


SUPERFICIAL    MUSCLES    OE    THE    BACK. 


17^ 


Fig.  139.  —  The  Superficial  Muscles  of  the  Back. 


372 


LATISSIMUS    DORSI. 


lumbar  and  lower  thoracic  regions,  and  thence  extends  to  the 
arm,  where  it  forms  part  of  the  posterior  boundary  of  the  axilla. 

^  It  arises  from  the  posterior  third  of  the  external  lip  of  the  crest 
of  the  ilium,  from  the  spinous  processes  of  the  two  upper  sacral, 
all  the  lumbar  and  the  six  lower  thoracic  vertebrae,  and  their 
supraspinous  ligament,  by  a  strong  aponeurosis  ;  and,  lastly, 
from  the  three  or  four  lower  ribs  by  fleshy  slips,  which  inter- 
digitate  with  those  of  the  external  oblique  muscle  of  the  abdo- 
men. All  the  fibres  converge  towards  the  axilla,  where  they 
form  a  thick  muscle,  which  curves  over  the  inferior  angle  of  the 

■  scapula,  and  is  inserted  by  a  broad,  flat  tendon  into  the  bottom 
of  the  bicipital  groove  of  the  humerus.  The  upper  fibres  are 
inserted  into  the  lowest  of  the  groove,  the  lower  fibres  into  the 
upper  part.  The  tendon  is  about  two  inches  (5  cm^  broad,  and 
lies  in  front  of  and  higher  than  that  of  the  pectoralis  major  and 
of  the  teres  major,  from  which  it  is  separated  by  a  large  bursa* 
It  is  supplied  mainly  by  the  long  subscapular  nerve,  also  by  the 
posterior  branches  of  the  thoracic  and  lumbar  nerves. 

The  latissimus  dorsi  draws  the  humerus  inwards,  downwards, 
and  backwards,  rotating  it  also  inwards.  It  co-operates  with 
the  pectoralis  major  in  pulling  any  object  towards  the  body  ;  if 
the  humerus  be  the  fixed  point,  it  raises  the  body,  as  in  climb- 
ing. The  object  of  the  muscle  arising  so  high  up  the  back  is, 
that  the  transverse  fibres  of  the  muscle  may  strap  down  the 
inferior  angle  of  the  scapula.  It  sometimes  happens  that  the 
scapula  slips  above  the  muscle  ;  this  displacement  is  readily 
recognized  by  the  unnatural  projection  of  the  lower  angle  of 
the  bone,  and  the  impaired  movements  of  the  arm.f 

The  muscle  covering  the  latissimus  dorsi  is  the  trapezius 
above  ;  those  lying  beneath  it  are,  a  small  part  of  the  rhom- 
boideus  major,  of  the  infraspinatus,  and  of  the  teres  major,  the 
serratus  posticus  inferior,  the  spinalis  dorsi,  the  longissimus 
dorsi,  the  ilio-costalis,  and  the  external  intercostals.  Between 
the  base  of  the  scapula,  the  trapezius,  and  the  upper  border  of 
the  latissimus  dorsi,  a  triangular  space  is  observed  when  the 

*  The  latissimus  dorsi  frequently  receives  a  distinct  accessory  slip  from  the 
inferior  angle  of  the  scapula. 

t  We  have  seen  several  instances  of  this  displacement.  There  is  great  pro- 
jection of  the  inferior  angle  of  the  scapula,  especially  when  the  patient  attempts  to 
raise  the  arm.  He  cannot  raise  the  arm  beyond  a  right  angle,  unless  fiiTn  pressure 
is  made  on  the  lower  angle  of  the  scapula,  so  as  to  supply  ihe  jjlace  of  the  muscu- 
lar strap.  Whether  the  scapula  can  be  replaced  or  not,  a  firm  bandage  should  be 
applied  round  the  chest. 


SPINAL    ACCESSORY    NERVE.  373 

arm  is  raised,  in  which  the  lower  fibres  of  the  rhomboideus 
major  and  part  of  the  sixth  intercostal  space  are  exposed.  Im- 
mediately above  the  crest  of  the  ilium,  between  the  free  margins 
of  the  latissimus  dorsi  and  external  oblique,  there  is,  also,  an 
interval  in  which  a  little  of  the  internal  oblique  can  be  seen. 

The  triangle  formed  by  the  outer  border  of  the  latissimus 
dorsi,  the  posterior  border  of  the  external  oblique,  and  the  crest 
of  the  ilium  between  them,  is  termed  Petit' s  triangle,  and  may 
be  the  seat  of  hernia.     (A.  H.) 

Lumbar  or  Vertebral  Aponeurosis.  —  This  dense  shining 
aponeurosis  of  the  back  (sometimes  termed  the  aponeurosis  of 
the  latissimus  dorsi)  forms  the  posterior  part  of  the  sheath  of 
the  erector  spinae.  It  is  pointed  above,  where  it  is  continuous 
with  the  deep  cervical  fascia,  broader  and  stronger  below.  It 
consists  of  tendinous  fibres,  which  are  attached  internally  to  the 
spines  of  the  thoracic,  all  the  lumbar  and  sacral  vertebrae ; 
externally,  to  the  angles  of  the  ribs ;  and  inferiorly  it  is  blended 
with  the  tendons  of  the  serratus  posticus  inferior  and  latissimus 
dorsi.  When  suppuration  takes  place  in  the  loins,  constituting 
a  lumbar  abscess  in  connection  with  spinal  disease,  the  pus  is 
seated  beneath  this  aponeurosis,  and  is  therefore  tardy  in  com- 
ing to  the  surface. 

Dissection.  —  Reflect  the  trapezius  from  its  insertion.  On 
its  under  surface  see  the  ramifications  of  its  nutrient  artery,  the 
S?iperjicialis  colli,  a  branch  of  the  posterior  scapular.  A  large 
nerve,  the  spinal  accessory,  enters  its  under  surface  near  the 
clavicle,  and  divides  into  filaments,  which,  reinforced  by  fila- 
ments from  the  third  and  fourth  cervical  nerves,  are  distributed 
to  the  muscle  as  far  as  its  lower  border. 

Spinal  Accessory  Nerve. — This  nerve,  the  eleventh  cere- 
bral nerve,  arises  by  two  roots  —  the  accessory  and  the  spinal 
portions  :  the  former  from  the  medulla,  the  latter  from  the  spi- 
nal cord.  The  accessory  portion,  the  smaller,  arises  by  four  or 
five  filaments  from  a  gray  nucleus  in  the  floor  of  the  fourth 
ventricle,  below  the  origin  of  the  pneumogastric  nerve  ;  the 
spinal  portion  arises  from  the  lateral  part  of  the  cervical  portion 
of  the  spinal  cord  by  several  filaments,  some  of  which  arise  as 
low  as  the  sixth  cervical  vertebra,  and  which  may  be  traced  into 
the  gray  matter  of  the  anterior  horn.  Formed  by  the  union  of 
these  roots,  the  nerve  enters  the  skull  through  the  foramen 
magnum,  and  leaves  it  again,  with  the  accessory  portion,  through 
the  foramen  jugulare.     These  portions  communicate  external  to 


374  RHOMBOIDEI. 

the  skull ;  but  while  the  accessory  root  joins  the  vagus,  the  spi- 
nal portion,  in  the  main,  runs  behind  the  internal  jugular  vein, 
traverses  obliquely  the  upper  third  of  the  sterno-mastoid  muscle, 
and  crosses  the  posterior  triangle  of  the  neck  to  the  trapezius, 
which  it  supplies  (p.  89).  In  front  of  the  trapezius  it  is  joined 
by  branches  from  the  third,  fourth,  and  fifth  cervical  nerves, 
together  with  which  it  communicates  with  the  posterior  branches 
of  the  spinal  nerves. 

The  trapezius  should  now  be  cut  through  the  middle,  and  the 
inner  half  turned  inwards  towards  the  spine,  the  outer  half  over 
the  clavicle  and  the  spine  of  the  scapula. 

Beneath  the  trapezius  we  have  to  examine  the  second  layer, 
consisting  of  three  muscles  connected  with  the  scapula  ;  namely, 
the  levator  anguli  scapulae,  the  rhomboideus  major  and  minor. 
The  scapula  should  be  adjusted  so  as  to  stretch  their  fibres. 

Levator  Anguli  Scapulae. — This  muscle  is  situated  at  the 
back  and  side  of  the  neck.  It  arises  by  four  tendons  from  the 
posterior  tubercles  of  the  transverse  processes  of  the  four  upper 
cervical  vertebrae.  The  muscular  slips  to  which  the  tendons 
give  rise  form  a  single  muscle,  which  descends  outwards  along 
the  side  of  the  neck,  and  is  inseited  into  the  posterior  border  of 
the  scapula  between  its  spine  and  superior  angle.  Its  action  is 
to  raise  the  posterior  superior  angle  of  the  scapula ;  thus  rotat- 
ing the  scapula  by  depressing  the  axillary  angle,  as,  for  in- 
stance, in  shrugging  the  shoulders.  Its  nerve  comes  from  the 
fifth  cervical,  and  by  filaments  from  the  external  series  of  the 
deep  cervical  plexus,  which  come  from  the  third  and  fourth 
cervical  nerves. 

Rhomboideus  Major  and  Minor.  —  These  flat  muscles  ex- 
tend from  the  spinous  processes  of  the  vertebrae  to  the  base  of 
the  scapula.  They  often  appear  like  a  single  muscle.  The 
rhomboideus  minor,  the  higher  of  the  two,  arises  by  a  thin 
aponeurosis  from  the  spinous  processes  of  the  last  cervical  and 
the  first  thoracic  vertebrae,  and  is  inserted  into  the  base  of  the 
scapula  opposite  its  spine.  The  rhomboideus  major  arises  by 
tendinous  fibres  from  the  spinous  processes  of  the  four  or  five 
upper  thoracic  vertebrae  and  the  supraspinous  ligament,  and  is 
inserted  by  fleshy  fibres  into  the  base  of  the  scapula  between  its 
spine  and  inferior  angle,  the  larger  number  of  the  fibres  being 
inserted  into  a  tendinous  arch,  which  is  chiefly  attached  to  the 
posterior  inferior  angle.  The  action  of  these  muscles  is  to  draw 
the  scapula  upwards  and  backwards.  They  are  the  antagonists 
of  the  serratus  magnus. 


SUBSCAPULAR    ARTERY.  375 

The  nerve  of  the  rhomboid  muscles  (posterior  scapular)  is  a 
branch  of  the  fifth  cervical.  It  passes  outwards  beneath  the 
lower  part  of  the  levator  anguli  scapulas,  to  which  it  sends  a 
branch,  and  is  lost  in  the  under  surface  of  the  rhomboidei. 

Omo-hyoideus.  —  This  muscle  extends  from  the  scapula  to 
the  OS  hyoides,  and  consists  of  two  long  narrow  muscular  por- 
tions, connected  by  an  intermediate  tendon  beneath  the  sterno- 
mastoid.  The  posterior  portion  only  can  be  seen  in  the  present 
dissection.  It  arises  from  the  upper  border  of  the  scapula,  close 
behind  the  notch,  and  from  the  transverse  ligament  above  the 
notch.  Thence  the  slender  muscle  passes  forward  across  the 
lower  part  of  the  neck,  beneath  the  sternoid-mastoid,  where  it 
changes  its  direction  and  ascends  nearly  vertically,  to  be  attached 
to  the  OS  hyoides  at  the  junction  of  the  body  with  the  greater 
cornu  (Fig.  3 7,  p.  95).  Thus  the  two  portions  of  the  muscle  form, 
beneath  the  sterno-mastoid,  an  obtuse  angle,  of  which  the  apex 
is  tendinous,  and  of  which  the  angular  direction  is  maintained 
by  a  layer  of  fascia,  proceeding  from  the  tendon  to  the  first  rib 
and  the  clavicle.  Its  action  is  to  depress  the  os  hyoides.  Its 
nerve  comes  from  the  descendens  hypoglossi  and  the  communi- 
cantes  hypoglossi  (pp.  1 19-124). 

Subscapular  Artery.  —  This  artery  (transversalis  humeri), 
a  branch  of  the  thyroid  axis  (Fig.  49,  No.  12,  p.  133),  runs  be- 
hind and  parallel  with  the  clavicle,  over  the  lower  end  of  the 
scalenus  anticus  and  subclavian  artery,  and  beneath  the  sterno- 
mastoid  and  omo-hyoid  muscles,  to  the  upper  border  of  the 
scapula,  where  it  usually  passes  above  the  ligament  bridging 
over  the  notch.  It  ramifies  in  the  supraspinous  fossa,  supplying 
the  supraspinatus,  and  then  passes  under  the  acromion  to  the 
infraspinous  fossa,  where  it  inosculates  freely  with  the  dorsalis 
scapulae,  a  branch  of  the  subscapular.      It  sends  off :  — 


a,  The  inferior  sterno-mastoid  artery  to  the  sterno-mastoid  and  contiguous  mus- 
cles ;  b,  the  supra-acrotnial  branch,  which  ramifies  upon  the  acromion,  anastomos- 
ing with  the  other  acromial  arteries  derived  from  branches  of  the  axillary;  c,  a. 
small  subscapular  branch  to  the  fossa  of  the  same  name  ;  d,  artiadar  arteries  to 
the  shoulder  joint ;  and,  lastly,  e,  the  infraspinous  branch,  which  anastomoses  ^\•ith 
the  dorsalis  scapulas.  The  suprascapular  vein  terminates  either  in  the  subclavian 
or  in  the  external  jugular. 

The  suprascapular  nerve,  a  branch  of  the  fifth  and  sixth  cervical  nerves,  runs 
WTith  the  corresponding  artery,  and,  after  passing  through  the  suprascapular  notch, 
is  distributed  to  the  supraspinatus  and  infraspinatus.  In  the  supraspinous  fossa, 
this  nerve  sends  a  small  articular  branch  to  the  shoulder-joint ;  in  the  infra- 
spinous fossa  it  gives  off  two  branches  to  the  infraspinatus,  and  some  to  the 
shoulder-joint. 


37^  SERRATUS    MAGNUS. 

Posterior  Scapular  Artery.  —  This  artery  is  one  of  the  di- 
visions of  the  transversalis  colli,  but  comes  very  frequently  from 
the  subclavian  in  the  third  part  of  its  course  (p.  135).  It  runs 
across  the  lower  part  of  the  neck,  above,  or  between  the  nerves 
of  the  brachial  plexus,  towards  the  posterior  superior  angle  of 
the  scapula.  Here  it  pursues  its  course  along  the  posterior 
border  of  the  scapula  beneath  the  levator  anguli  scapulae  and 
the  rhomboidei,  anastomosing  with  branches  of  the  suprascapular 
and  subscapular  arteries,  and  with  branches  from  the  intercostal 
arteries.  The  corresponding  vein  joins  the  external  jugular  or 
the  subclavian. 

Dissection.  —  Divide  the  rhomboid  muscles  near  their  inser- 
tion, and  trace  the  artery  to  the  inferior  angle  of  the  scapula, 
where  it  terminates  in  the  rhomboidei,  serratus  magnus,  and 
latissimus  dorsi. 

Numerous  muscular  branches  arise  from  the  posterior  scapular. 
The  supcrficialis  colli  (the  other  division  of  the  transversalis  colli) 
is  given  off  near  the  upper  angle  of  the  scapula  for  the  supply 
of  the  trapezius,  which  it  enters  together  with  the  spinal  acces- 
sory nerve. 

Divide  and  reflect  the  latissimus  dorsi  below  the  inferior 
angle  of  the  scapula,  and  draw  the  scapula  forcibly  outwards,  to 
have  a  more  perfect  view  of  the  extent  of  the  serratus  magnus 
than  was  seen  in  the  axilla.  The  abundance  of  connective 
tissue  in  this  situation  is  necessary  for  the  play  of  the  scapula 
on  the  chest. 

Serratus  Magnus.  —  This  broad,  thin,  flat  muscle  intervenes 
between  the  scapula  and  the  ribs.  It  arises  by  nine  fleshy  digi- 
tations  from  the  eight  upper  ribs,  each  rib  giving  origin  to  one, 
and  the  second  to  two,  and  from  the  fascia  covering  the  corre- 
sponding intercostal  spaces.  The  four  lower  digitations  cor- 
respond with  those  of  the  external  oblique  muscle  of  the 
abdomen.  The  fibres  pass  backwards  and  outwards  and  are 
arranged  in  three  fasciculi ;  the  upper  portion  arises  from  the 
first  and  second  ribs  and  the  fascia  between  them,  and  is  inserted 
into  the  triangular  surface  in  front  of  the  upper  angle  of  the 
scapula ;  the  middle  portion  arises  from  the  second,  third,  and 
fourth  ribs,  and  is  inserted  into  the  inner  lip  of  the  vertebral 
border  between  the  first  and  third  portions ;  the  third  portion 
arises  from  the  fifth,  sixth,  seventh,  and  eighth  ribs,  and  is 
inserted  into  the  smooth  surface  in  front  of  the  inferior  angle  ; 
this  last  portion  consists  of  four  serrations,  and  are  those  which 
interdigitate  with  the  external  oblique. 


DISSECTION    OF    THE    MUSCLES    OF    THE    SHOULDER.         3/7 

This  is  the  most  important  of  the  muscles  which  regulate  the 
movements  of  the  scapula.  It  draws  the  scapula  forwards,  and 
thus  gives  additional  reach  to  the  arm  ;  it  counteracts  all  forces 
which  tend  to  push  the  scapula  backwards  ;  for  instance,  when 
a  man  falls  forwards  upon  his  hands,  the  serratus  magnus  sus- 
tains the  shock  and  prevents  the  scapula  from  being  driven 
back  to  the  spine.  Supposing  the  fixed  point  to  be  at  the 
scapula,  some  anatomists  ascribe  to  it  the  power  of  raising  the 
ribs  ;  hence  Sir  Charles  Bell  called  it  the  external  respiratory 
muscle,  the  internal  respiratory  muscle  being  the  diaphragm. 

The  nerve  which  supplies  it  is  a  branch  of  the  fifth  and  sixth 
cervical  nerve ;  it  descends  along  its  outer  surface,  distributing 
a  filament  to  each  digitation  of  the  muscle  (p.  139). 

Dissection.  —  Divide  the  serratus  magnus  near  the  scapula, 
and  remove  the  arm  by  sawing  through  the  middle  of  the 
clavicle,  cutting  through  the  axillary  vessels  and  nerves.  These 
should  be  tied  to  the  coracoid  process.  After  the  removal  of 
the  arm  examine  the  precise  insertions  of  the  preceding  muscles. 

DISSECTION    OF   THE    MUSCLES    OF   THE 
SHOULDER. 

Dissection.  —  The  remainder  of  the  skin  over  the  shoulder  is 
to  be  reflected,  and  in  the  subcutaneous  tissue  are  found  the 
cutaneous  vessels  and  nerves.  Some  pass  down  over  the 
shoulder,  others  ascend  over  the  deltoid,  emerging  from  beneath 
its  lower  border. 

The  acromial  brandies  come  from  the  third  and  fourth  cervi- 
cal nerves,  and  descend  over  the  acromion  (Fig.  140)  in  front 
of  and  behind  the  deltoid.  The  cutaneous  brajich  of  the  circum- 
flex nerve  comes  out  beneath  the  posterior  border  of  the 
deltoid,  and  supplies  the  skin  over  the  posterior  and  outer 
two-thirds  of  the  muscle ;  others  perforate  the  muscle,  each 
accompanied  by  a  small  artery. 

Notice  the  strong  layer  of  facia  upon  the  surface  of  the  del- 
toid, which  extends  from  the  aponeurosis  covering  the  muscles 
on  the  back  of  the  scapula,  and  is  continuous  with  the  fascia  of 
the  arm.  It  dips  down  between  the  fibres  of  the  muscle,  di- 
viding it  into  large  bundles.  This  fascia  is  to  be  removed  by 
putting  the  deltoid  on  the  stretch  and  reflecting  it  in  the  direc- 
tion of  its  fibres,  beginning  from  the  front.  The  fascia  will  be 
seen  to  be  continuous  in  front  with  the  fascia  covering  the  pec- 


3/8 


ACTION    OF    THE    DELTOID. 


toralis  major ;  above,  it  is  attached  to  the  clavicle  and  spine  of 
the  scapula  ;  behind,  it  is  continuous  with  that  over  the  infra- 
spinatus. 

Deltoid. — The  large  muscle  which  covers 
the  shoulder-joint  is  named  deltoid  from  its  re- 
semblance to  the  Greek  V  reversed.  It  arises 
from  the  external  third  of  the  anterior  border 
of  the  clavicle,  from  the  apex  and  outer  border 
of  the  acromion,  and  from  the  lower  border  of 
the  spine  of  the  scapula  down  to  the  triangular 
surface  at  its  root.  This  origin,  which  corre- 
sponds to  the  insertion  of  the  trapezius,  is  ten- 
dinous and  fleshy  everywhere,  except  at  the 
commencement  of  the  spine  of  the  scapula, 
where  it  is  simply  tendinous,  and  connected 
with  the  infraspinous  aponeurosis.  The  mus- 
cular fibres  descend,  the  anterior  backwards, 
the  posterior  forwards,  the  middle  perpendicu- 
larly ;  all  converge  to  a  tendon  which  is  in- 
serted into  a  rough  surface  on  the  outer  side 
of  the  humerus,  a  little  above  the  middle  of 
the  shaft  (Figs.  124  and  132,  pp.  324,  339). 
The  insertion  of  the  tendon  extends  one  inch 
and  a  half  ( J.(5*  cin>j  along  the  humerus,  and 
terminates  in  a  V-shaped  form,  the  origin  of 
the  brachialis  anticus  embracing  it  on  either 
side.  Sometimes  a  few  fibres  of  the  pectoralis 
major  are  connected  with  its  front  border. 

The  muscular  bundles  composing  the  deltoid 
have  a  peculiar  arrangement,  a  peculiarity  aris- 
ing from  its  broad  origin  and  its  narrow  in- 
sertion. It  consists  in  the  interposition  of 
tendons  between  the  bundles  for  the  attach- 
ment of  the  muscular  fibres.  The  annexed 
woodcut  shows  this  arrangement  better  than 
any  description.  The  action  of  the  muscle  is 
not  only  concentrated  upon  one  point,  but  its  power  is  also 
greatly  increased  by  this  arrangement. 

Action  of  the  Deltoid.  —  It  raises  the  arm  ;  but  it  can- 
not do  so  beyond  an  angle  of  ninety  degrees.  The  eleva- 
tion of  the  arm  beyond  this  angle  is  effected  through  the 
raising  of  the  shoulder  by  the  trapezius  and  scrratus  magnus. 


Fig.  140. —  Cutaneous 
Nekvesofthe  Left 
Shoulder  and  Arm. 
(Posterior  View.) 

I .  Supra-acromial  br. 
of  the  cervical  nerves. 
2.  Ascending  and  de- 
scending brs.  of  the 
circumflex  n.  3,  4. 
Cutaneous  brs.  of  the 
musculo-cutaneous  n. 
5.  Internal  cutaneous 
br.  of  musculo-spiral 
n.  6.  Intercosto-hu- 
meral  brs.  7.  Fila- 
ments of  the  lesser 
internal  cutaneous  n. 
8.  Posterior  cutaneous 
br.  of  internal  cutane- 
ous n.  9.  Uranch  of 
internal  cutaneous  n. 


BURSA    UNDER    THE    DELTOID. 


379 


Its  anterior  fibres  draw  the  arm  forwards ;  its  posterior,  back- 
wards. 

This  powerful  muscle  is  supplied  with  blood  by  the  anterior 
and  posterior  circumflex,  the  thoracica  humeraria,  the  thoracica 
acromialis,  all  from  the  axillary 
artery  ;  also  by  the  deltoid  branch 
of  the  brachial.  Its  no've  is  the 
circumflex. 

The  rotundity  of  the  shoulder 
is  due  not  so  much  to  the  deltoid 
as  to  the  upper  end  of  the  hu- 
merus. When  the  head  of  the 
humerus  is  dislocated  into  the 
axilla,  the  fibres  of  the  muscle 
run  vertically  to  their  insertion  ; 
hence  the  flattening  of  the  del- 
toid and  the  greater  prominence 
of  the  acromion. 

It  is  below  the  deltoid  that  an 
ununited  fracture  of  the  humerus 
is  most  commonly  met  with,  owing 
to  the  muscle  displacing  the 
upper  fragment. 

Dissection.  —  Reflect  the  deltoid  from  its  origin,  and  turn 
it  downwards.  Observe  the  ramifications  of  the  circumflex 
nerve  and  the  anterior  and  posterior  circumflex  arteries  on  its 
under  surface ;  notice  also  the  large  bursa  between  it  and  the 
tendons  inserted  into  the  great  tuberosity  of  the  humerus. 

Parts  Covered  by  the  Deltoid. — The  structures  seen  on 
reflecting  the  deltoid  are  as  follows  :  the  bursa  already  alluded 
to,  the  coracoid  process,  the  coraco-acromial  ligament,  the  ori- 
gins of  the  biceps,  and  coraco-brachialis,  the  insertions  of  the 
pectoralis  minor  and  major,  the  long  head  or  the  biceps, 
the  insertions  of  the  supra-spinatus,  infraspinatus,  and  teres 
minor,  the  long  and  external  heads  of  the  triceps,  the  cir- 
cumflex vessels  and  nerve,  and  the  neck  and  upper  part  of  the 
humerus. 

Bursa  under  the  Deltoid,  or  Subacromial.  —  The  large 
bursa  under  the  deltoid  extends  for  some  distance  beneath  the 
acromion  and  the  coraco-acromial  ligament,  and  covers  the  ten- 
dons attached  to  the  great  tuberosity  of  the  humerus.  It  com- 
municates, very  rarely,  with  the  shoulder-joint.     Its  use  is  to 


Fig.  141 — Analysis  of  the  Deltoid. 


38o 


POSTERIOR    CIRCUMFLEX    ARTERV 


facilitate   the  movements  of  the  head  of  the  bone   under  the 
acromial  arch. 

Posterior    Circumflex  Artery.  —  This  artery  is  given    off 
from  the  axillary  in  the  third  part  of  its  course ;    it  runs  behind 


Fig.  142. —  Triceps  Muscle. 

Triceps.  2.  Long  head  of  the  triceps. 
3.  Outer  liead.  4.  Innerhead.  5.  Tendon 
of  the  triceps.  6.  Its  attachment  to  the 
olecranon.  7.  Anconeus,  the  fibres  of 
which  follow  those  of  the  outer  head  of  the 
triceps.  8,8.  Superior  part  of  the  deltoid  ; 
the  posterior  half  has  been  excised,  g.  Its 
inferiorpart.  10.  Supra-spinatus.  11.  Infra- 
spinatus. 12.  Origin  of  the  teres  minor. 
13.  Insertion  of  the  teres  minor.  14.  Teres 
major.  15.  Superior  extremity  of  tl>e 
latissimus  dorsi.  16.  .Supinator  loneus  or 
brachio-radialis.  17.  Extensor  carpi  radi- 
alis  longior.  18.  Kxtensor  carjji  ulnaris. 
19.    F'lexor  carpi  ulnaris. 


E..SALLC9. 
Fig.  143.  —  Anterior  Muscles  of  the  Arm. 

I.  Biceps.  2.  Short  head  of  the  biceps.  3.  Long 
head  of  the  same.  4.  Tendon  attached  to 
the  tuberosity  of  the  radius.  5.  Semilunar 
fascial  aponeurosis  of  the  biceps.  5.  Coraco- 
brachialis.  7,8.  The  two  portions  of  the 
pectoralis  major  forming  a  groove  with  its 
concavity  above.  9.  Attachment  of  the 
latissimus  dorsi.  19.  Teres  major.  11 .  Sub- 
scapularis.  12.  P.rachialisanticus.  13.  Long 
head  of  the  triceps.  14.  Internal  head 
of  the  triceps.  15.  Supinator  longus  or 
brachio-radialis.  16.  Extensor  carpi  radi- 
alis  longior. 


MUSCLES    OF    THE    SHOULDER.  38 1 

the  surgical  neck  of  the  humerus,  through  a  quadrilateral  open- 
ing, bounded  above  by  the  subscapularis  and  teres  minor ;  be- 
low, by  the  teres  major  ;  externally,  by  the  neck  of  the  humerus; 
and  internally,  by  the  long  head  of  the  triceps  (p.  380).  Its 
branches  terminate  on  the  under  surface  of  the  deltoid,  anasto- 
mosing with  the  anterior  circumflex,  acromial  thoracic,  and 
suprascapular  arteries. 

From  the  posterior  circumflex  a  branch  descends  in  the  sub- 
stance of  the  long  head  of  the  triceps,  to  inosculate  with  the 
superior  profunda ;  this  is  one  of  the  channels  through  which 
the  circulation  would  be  carried  on  if  the  axillary  were  tied  in 
the  last  part  of  its  course. 

Circumflex  Nerve.  — This  nerve,  a  branch  of  the  posterior 
cord  of  the  brachial  plexus,  runs  with  the  posterior  circumflex 
artery  through  the  same  quadrilateral  space,  and  then  divides 
into  two  branches  —  an  upper  and  a  lower.  The  upper  branch 
winds  round  the  neck  of  the  humerus  and  supplies  the  anterior 
part  of  the  deltoid,  and  gives  off  cutaneous  branches  to  supply 
the  skin  over  its  lower  part.  The  lozvcr  branch  sends  a  filament 
to  the  teres  minor,  one  or  two  to  the  integuments  over  the 
shoulder  at  its  posterior  part,  and  terminates  in  the  substance 
of  the  deltoid.  It  also  distributes  an  articular  filament,  which 
enters  the  shoulder-joint  in  front,  below  the  subscapularis. 

The  proximity  of  this  nerve  to  the  head  of  the  humerus  ex- 
plains the  occasional  paralysis  of  the  deltoid,  after  dislocation  or 
fracture  of  the  humerus.  The  nerve  is  liable  to  be  injured,  if 
not  actually  lacerated,  by  the  pressure  of  the  bone. 

A  strong  aponeurosis  covers  the  muscles  of  the  dorsum  of 
the  scapula,  and  is  firmly  attached  to  the  spine  and  borders  of 
the  bone.  At  the  dorsal  edge  of  the  deltoid  it  divides  into 
two  layers,  one  of  which  passes  over,  the  other  under,  the 
muscle.  Remove  the  aponeurosis,  so  far  as  it  can  be  done 
without  injury  to  the  muscular  fibres  which  arise  from  its  under 
surface. 

Infra-spinatus.  —  This  triangular  muscle  arises  by  fleshy 
fibres  from  the  posterior  two-thirds  of  the  infraspinous  fossa, 
and  by  tendinous  fibres  from  the  ridges  on  the  fossa,  and 
from  the  aponeurosis  which  covers  it.  The  fibres  converge  to  a 
tendon,  which  is  at  first  contained  in  the  substance  of  the  muscle, 
and  then  proceeds  over  the  capsular  ligament  of  the  shoulder- 
joint,  to  be  inserted  into  the  middle  depression  on  the  greater 
tuberosity  of  the  humerus.  Its  nerve  comes  from  the  supra- 
scapular. 


382  MUSCLES  OF  THE  SHOULDER. 

Teres  Minor.  —  This  long,  narrow  muscle  is  situated  below 
the  infraspinatus,  along  the  inferior  border  of  the  scapula.  It 
arises  from  the  dorsum  of  the  scapula  close  to  the  axillary  bor- 
der, and  from  the  intermuscular  septa  between  it  and  the  infra- 
spinatus above  and  the  teres  major  below.  The  fibres  ascend 
outwards  parallel  with  those  of  the  infraspinatus,  and  terminate 
in  a  tendon,  which  passes  over  the  capsular  ligament  of  the 
shoulder-joint,  and  is  inserted  into  the  lowest  depression  on  the 
great  tuberosity  of  the  humerus,  and  by  muscular  fibres  into 
the  bone  below  it.  It  is  supplied  by  a  branch  of  the  circumflex 
nerve,  which  enters  the -muscle  at  its  lower  border,  and  it  has 
(usually)  a  small  ganglion-like  enlargement  upon  it. 

The  action  of  the  infraspinatus  and  teres  minor  is  to  rotate 
the  humerus  outwards,  and  when  the  arm  is  raised  it  draws  the 
humerus  downwards  and  backwards. 

Teres  Major.  —  This  muscle  is  closely  connected  with  the 
latissimus  dorsi,  and  extends  from  the  inferior  angle  of  the 
scapula  to  the  humerus,  contributing  to  form  the  posterior 
boundary  of  the  axilla.  It  arises  from  the  flat  surface  on  the 
dorsal  aspect  of  the  inferior  angle  of  the  back  of  the  scapula, 
from  its  axillary  border,  and  the  intermuscular  septa,  and  termi- 
nates in  a  flat  tendon,  nearly  two  inches  (5«^^2-)  in  breadth, 
which  is  inserted  into  the  inner  edge  of  the  bicipital  groove  of 
the  humerus,  behind  and  a  little  lower  than  the  tendon  of  the 
latissimus  dorsi.  Its  action  is  to  draw  the  humerus  backwards 
and  downwards  when  the  arm  is  raised,  and  to  rotate  it  slightly 
inwards.  It  is  supplied  by  the  middle  subscapular  nerve,  which 
enters  it  on  its  axillary  aspect. 

A  bursa  is  found  in  front  of,  and  another  behind,  the  tendon 
of  the  teres  major;  the  former  separates  it  from  the  latissimus 
dorsi,  the  latter  from  the  bone. 

Supra-spinatus. —  This  muscle  «mri- from  the  posterior  two- 
thirds  of  the  supraspinous  fossa,  and  from  its  aponeurotic  cover- 
ing. It  passes  under  the  acromion,  over  the  capsular  ligament 
of  the  shoulder-joint,  and  is  inserted  by  a  strong  tendon  into 
the  superior  depression  on  the  greater  tuberosity  of  the  humerus. 
To  see  its  insertion,  the  acromion  should  be  sawn  off  near  the 
neck  of  the  scapula.  Its  action  is  to  assist  the  deltoid  in  rais- 
ing the  arm.  It  is  supplied  by  two  branches  derived  from  the 
subscapular  nerve. 

Subscapularis.  — This  triangular  fleshy  muscle  occupies  the 
subscapular  fossa.      It  arises  from  the  posterior  three-fourths  of 


DORSALIS    SCAPULA    ARTERY.  383 

the  fossa,  except  the  vertebral  border  and  angles  which  give 
attachment  to  the  serratus  magnus,  and  from  three  or  four  tendi- 
nous septa  attached  to  the  oblique  bony  ridges  on  its  surface. 
The  fibres,  passing  upwards  and  outwards,  converge  towards 
the  neck  of  the  scapula,  where  they  terminate  in  three  or 
four  tendons,  which  are  concealed  amongst  the  muscular  fibres, 
and  are  inserted  into  the  lesser  tuberosity  of  the  humerus  and 
into  the  bone  for  an  inch  below  the  tuberosity.  Its  broad  in- 
sertion is  closely  connected  with  the  capsule  of  the  shoulder- 
joint,  which  it  completely  protects  upon  its  inner  side.  Its  action 
is  to  rotate  the  humerus  inwards,  and,  when  the  arm  is  raised, 
draws  it  downwards.  The  nerves  which  supply  it  come  from 
the  long  and  middle  subscapular  nerves. 

The  coracoid  process,  with  the  coraco-brachialis  and  short 
head  of  the  biceps,  forms  an  arch,  under  which  the  tendon  of 
the  subscapularis  plays.  There  are  several  bnrsce  about  the 
tendon.  One,  of  considerable  size,  on  the  upper  surface  of  the 
tendon,  facilitates  its  motion  beneath  the  coracoid  process  and 
the  coraco-brachialis ;  this  sometimes  communicates  with  the 
large  bursa  under  the  deltoid.  Another  is  situated  between 
the  tendon  and  the  capsule  of  the  joint,  and  almost  invariably 
communicates  with  it. 

Dissection.  —  Now  reflect  the  muscles  from  the  surfaces  of 
the  scapula,  to  trace  the  arteries  which  ramify  upon  it. 

Continuation  of  Suprascapular  Artery  and  Nerve. — This 
artery,  a  branch  of  the  thyroid  axis,  runs  under  and  parallel 
with  the  clavicle,  and  passes  above  the  notch  of  the  scapula 
into  the  supraspinous  fossa  ;  it  sends  a  branch  to  the  supraspi- 
natus,  another  to  the  shoulder-joint,  and  then  descends  behind 
the  neck  of  the  scapula  into  the  fossa  below  the  spine,  where  it 
inosculates  directly  with  the  dorsalis  scapulae.  Its  branches 
ramify  upon  the  bone,  and  supply  the  infraspinatus  and  teres 
minor  (Fig.  144). 

The  suprascapular  nerve  passes  most  frequently  through  the 
notch  of  the  scapula,  accompanies  the  corresponding  artery, 
supplies  two  branches  to  the  supraspinatus  and  one  to  the 
shoulder-joint  ;  it  then  enters  the  infraspinous  fossa,  to  termi- 
nate in  the  infraspinatus. 

Dorsalis  Scapulae  Artery. — This  artery,  after  passing 
through  the  triangular  space  (p.  319),  curves  round  the  inferior 
border  of  the  scapula,  which  it  grooves,  to  the  infraspinous 
fossa,  where  it  ascends  close  to  the  bone,  and  anastomoses  with 


384 


DORSALIS    SCAPUL.E    ARTERY. 


the  supra  and  posterior  scapular  arteries.  Another  branch  of 
the  subscapular  artery  runs  between  the  teres  minor  and  major 
towards  the  inferior  angle  of  the  scapula,  where  it  anastomoses 
with  the  posterior  scapular  artery  (Fig.  144). 

The  several  communications  above  the  scapula,  between  the 
branches  of  the  subclavian  and  axillary  arteries,  would  furnish 
a  large  collateral  supply  of  blood  to  the  arm,  if  the  subclavian 
were  tied  above  the  clavicle  (p.  137). 


Fig.  144.  —  Diagram  of  Arteries  of  Scapula. 

I.  Suprascapular  artery.      2.    Posterior   citcumflex  a.      3.    Infraspinous    br.  of    suprascapular  a. 

4     Dorsalis  scapulae  a.     5.    Posterior  scapular  a,     6.  Subclavian  a. 

Dissection.  —  If  the  skin  has  not  been  reflected  from  the 
back  of  the  arm  it  should  now  be  done.  In  the  subcutaneous 
tissue  will  be  seen  the  hiternal  cntaricous  branch  of  the  imismlo- 
spiral  nerve,  which  supplies  the  skin  as  low  down  as  the  ole- 
cranon. On  the  inner  side  of  this  branch  is  the  intercosto- 
humeral  nerve,  supplying  the  skin  as  far  as  the  lower  third  of 
the  arm.  The  nerve  of  Wrisb erg  ?\?>o  supplies  the  lower  third 
of  the  arm  ;  and  on  the  outer  side  for  the  same  distance  is  the 
external  cutaneous  branch  of  the  muscitlo-spiral  x\qx^q. 


TRICEPS    EXTENSOR    CUBITI.  385 

The  fascia  is  now  to  be  removed,  when  the  triceps  will  be  ex- 
posed, forming  the  only  muscle  on  the  back  of  the  arm. 

Triceps  Extensor  Cubiti.  —  This  muscle,  which  arises  by 
three  distinct  heads,  and  was  only  partially  seen  in  the  dissec- 
tion of  the  upper  arm  (p.  339),  should  now  be  thoroughly 
examined  (Fig.  143,  p.  380).  The  /o7i£-  /icad  arises  immediately 
below  the  glenoid  cavity  of  the  scapula,  by  a  strong,  flat  tendon, 
which  is  connected  with  the  capsular  and  glenoid  ligaments  of 
the  shoulder-joint.  The  external  head  arises  from  the  posterior 
part  of  the  humerus,  below  the  insertion  of  the  teres  minor,  as 
far  as  the  musculo-spiral  groove,  from  the  outer  border  of  the 
humerus,  and  the  external  intermuscular  septum.  The  internal 
head  arises  from  the  posterior  part  of  the  humerus,  below  the 
teres  major  and  the  musculo-spiral  groove,  as  far  as  the  ole- 
cranon fossa  ;  it  has  an  additional  origin  from  the  internal  inter- 
muscular septum,  and  from  the  internal  border  of  the  humerus. 
The  precise  origin  of  these  heads  from  the  humerus  may  be 
ascertained  by  following  the  superior  profunda  artery  and 
musculo-spiral  nerve,  which  separate  them.  The  three  portions 
of  the  muscle  terminate  upon  a  broad  tendon,  which  covers  the 
back  of  the  elbow-joint,  and  is  inserted  into  the  summit  and 
sides  of  the  olecranon  ;  it  is  also  connected  with  the  fascia  on 
the  back  of  the  forearm.  The  effect  of  this  connection  is  that 
the  same  muscle  which  extends  the  forearm  tightens  the  fascia 
which  gives  origin  to  the  extensors  of  the  wrist  and  fingers. 
The  same  holds  good  in  the  case  of  the  biceps,  and  its  semilu- 
nar expansion  in  the  fascia  of  the  forearm. 

Between  the  tendon  and  the  olecranon  is  a  biirsa,  commonly 
of  small  size,  but  sometimes  so  large  as  to  extend  upwards  be- 
hind the  capsule  of  the  joint.  This  bursa  must  not  be  mis- 
taken for  the  subcutaneous  one,  which  is  situated  between  the 
skin  and  the  olecranon,  and  is  so  often  injured  by  a  fall  on  the 
elbow. 

Dissection. — By  dividing  the  triceps  transversely  a  little 
above  the  elbow,  and  turning  down  the  lower  portion,  it  will  be 
seen  that  some  of  the  muscular  fibres  terminate  upon  the  cap- 
sular ligament  of  the  joint.  They  have  been  described  as  a 
distinct  muscle,  under  the  name  of  the  siibanconcns ;  their  use 
is  to  draw  up  the  capsule  so  that  it  may  not  be  injured  during 
extension  of  the  arm.  The  subanconeus  is,  in  this  respect, 
analagous  to  the  subcrureus  muscle  of  the  thigh.  Observe 
the  bursa  under  the  tendon,  and  the  arterial  arch  formed  upon 


386  DISSECTION    OF    THE    BACK    OF    THE    FOREARM. 

the  back   part   of  the  capsule  by  the  superior  profunda  and  the 
anastomotica  magna  (Fig.  147,  p.  396). 

Trace  the  continuation  of  the  superior  prof unda  artery  (p.  334) 
and  musculo-spiral  nerve  round  the  posterior  part  of  the  hume- 
rus. They  lie  in  a  slight  groove  on  the  bone,*  between  the  ex- 
ternal and  internal  heads  of  the  triceps,  and  are  protected  by 
an  aponeurotic  arch  thrown  over  them  by  the  external  head  of 
the  triceps.  After  supplying  the  muscles,  the  artery  continues 
its  course  along  the  outer  side  of  the  arm  between  the  brachialis 
anticus  and  supinator  radii  longus,  and  inosculates  with  the 
radial  recurrent.  It  gives  off  a  branch,  which  runs  down  be- 
tween the  triceps  and  the  bone,  and  inosculates,  at  the  back  of 
the  elbow,  with  the  anastomotica  magna  and  posterior  interos- 
seous recurrent.  The  musculo-spiral  nerve  which  accompanies 
the  artery  sends  branches  to  supply  the  three  portions  of  the 
triceps,  the  supinator  radii  longus  or  brachio-radialis,  and  ex- 
tensor carpi  radialis  longior.f  It  then  divides  into  the  poste- 
rior interosseous  and  radial  nerves.  The  small  nerve  must  be 
made  out  which  runs  down  in  the  substance  of  the  triceps, 
accompanied  by  a  branch  from  the  superior  profunda  artery,  to 
supply  the  anconeus.  The  cutaneous  branches  of  the  musculo- 
spiral  nerve  have  been  already  dissected  (p.  327). 

DISSECTION    OF    THE    BACK    OF    THE    FOREARM. 

Subcutaneous  Bursse.  —  Remove  the  skin  from  the  back 
of  the  forearm,  hand,  and  fingers,  and  make  out  the  subcutane- 
ous bursa  over  the  olecranon.  It  is  of  considerable  size,  and,  if 
distended,  would  appear  nearly  as  large  as  a  walnut.  Another 
buisa  is  sometimes  found  a  little  lower  down  upon  the  ulna. 
A  subcutaneous  bursa  is  generally  placed  over  the  internal 
condyle,  another  over  the  external.  A  bwsa  is  also  situated 
over  the  styloid  process  of  the  ulna  ;  this  sometimes  communi- 
cates with  the  sheath  of  the  extensor  carpi  ulnaris.  Small 
bursce  are  sometimes  developed  in  the  cellular  tissue  over  each 
of  the  knuckles. 

The  cutaneous  veins  from  the  back  of  the  hand  and  forearm 
join  the  venous  plexus  at  the  bend  of  the  elbow  (see  p.  327). 

*  It  is  worth  remembering  that  the  nerve  may  be  injured  by  a  fracture  of  the 
humerus  in  this  situation,  and  even  by  too  tight  l)andaging ;  the  result  being 
paralysis  of  the  extensor  muscles  of  the  forearm. 

t  The  brachialis  anticus  usually  receives  a  branch  from  the  musculo-spiral 
nerve. 


POSTERIOR    ANNULAR    LIGAMENT.  387 

Cutaneous  Nerves  of  the  Back  of  the  Forearm.  —  The 

cutaneous  nerves  of  the  back  of  the  forearm  are  derived  from 
the  external  cutaneous  branches  of  the  musculo-spiral,  from 
branches  of  the  internal  cutaneous,  and  of  the  external  cutane- 
ous nerves.  The  greater  number  of  these  nerves  may  be  traced 
down  to  the  back  of  the  wrist. 

Nerves  on  the  Back  of  the  Hand  and  Fingers.  —  The 
skin  on  the  back  of  the  hand  is  united  to  the  subjacent  tendons 
by  an  abundance  of  loose  connective  tissue,  in  which  are  large 
veins,  and  branches  of  the  radial  and  ulnar  nerves.  The  dorsal 
branch  of  the  ulnar  nerve  passes  beneath  the  tendon  of  the 
flexor  carpi  ulnaris,  pierces  the  fascia  just  above  the  wrist-joint, 
runs  over  the  posterior  annular  ligament  of  the  wrist,  and  di- 
vides upon  the  back  of  the  hand  into  filaments,  which  supply 
both  sides  of  the  back  of  the  little  finger,  the  ring  finger,  and 
the  ulnar  side  of  the  middle  finger.  The  radial  neri'e  passes 
obliquely  beneath  the  tendon  of  the  brachio-radialis,  perforates 
the  fascia  about  two  inches  (5  cm.)  above  the  wrist-joint,  and 
subdivides  into  filaments,  which  supply  both  sides  of  the  back  of 
the  thumb  and  forefinger,  and  the  radial  side  of  the  middle 
finger.*     (Fig.  135,  p.  350.) 

The  radial  nerve  commonly  gives  off,  on  the  back  of  the 
hand,  a  branch  which  joins  the  nearest  branch  of  the  ulnar. 

Fascia  on  Back  of  Forearm.  •—  The  fascia  on  the  back  of 
the  forearm  is  composed  of  fibres  interlacing  and  stronger  than 
that  upon  the  front  of  the  forearm.  It  is  attached  to  the  con- 
dyles of  the  humerus  and  to  the  olecranon,  and  is  strengthened 
by  an  expansion  from  the  tendon  of  the  triceps.  Along  the 
forearm  it  is  attached  to  the  ridge  on  the  posterior  part  of  the 
ulna.  Its  upper  third  gives  origin  to  the  fibres  of  the  muscles 
beneath  it,  and  divides  them  by  septa,  to  which  their  fibres  are 
also  attached. 

Posterior  Annular  Ligament.  —  This  ligament  should  be 
considered  as  a  part  of  the  fascia  of  the  forearm,  specially 
strengthened  by  oblique  aponeurotic  fibres  on  the  back  of  the 
wrist,  to  confine  the  extensor  tendons.     These  fibres  are  at- 

*  The  relative  share  which  the  radial  and  ulnar  nerves  take  in  supplying  the 
fingers  varies.  Under  any  arrangement  the  thumb  and  each  finger  has  two  dorsal 
nerves,  one  on  either  side,  of  which  the  terminal  branches  reach  the  root  of  the 
nail.  They  supply  filaments  to  the  skin  on  the  back  of  the  finger,  and  have  fre- 
quent communications  with  the  palmar  digital  nerves.  In  some  instances  one  or 
more  of  the  dorsal  nerves  do  not  extend  beyond  the  first  phalanx ;  their  place  is 
then  supplied  by  a  branch  from  the  palmar  nerve. 


388   SUPERFICIAL  MUSCLES  ON  THE  BACK  OF  THE  FOREARM. 

tached  to  the  outer  margin  of  the  radius,  and  thence  pass 
obliquely  inwards  to  the  inner  side  of  the  wrist,  where  they  are 
connected  with  the  pisiform  and  cuneiform  bones.  They  pass 
below  the  styloid  process  of  the  ulna,  to  which  they  are  in  no 
way  attached,  otherwise  the  rotation  of  the  radius  would  be 
impeded. 

Separate  Sheaths  for  Extensor  Tendons.  —  From  the  deep 
surface  of  the  posterior  annular  ligament,  processes  are  attached 
to  the  ridges  on  the  back  of  the  radius,  so  as  to  form  six  distinct 
fibro-osseous  sheaths  for  the  passage  of  the  extensor  tendons. 
Commencing  from  the  radius,  the  first  sheath  contains  the  ten- 
dons of  the  extensor  ossis  metacarpi  and  the  extensor  brevis  pol- 
licis  or  extensor  primi  mternodii  pollicis;  the  second,  the  tendons 
of  the  extensor  carpi  radialis  longior  and  brevior ;  the  third,  the 
tendon  of  the  extensor  longus  pollicis  or  extensor  secundi  inter- 
nodii  pollicis  ;  the  fourth,  the  tendons  of  the  extensor  indicis 
and  the  extensor  communis  digitorum  ;  the  fifth,  the  tendon  of 
the  extensor  minimi  digiti ;  and  the  sixth,  the  tendon  of  the 
extensor  carpi  ulnaris.  All  the  sheaths  are  lined  by  synovial 
membranes,  which  extend  nearly  to  the  insertions  of  their  ten- 
dons. Occasionally,  but  not  often,  one  or  more  of  them  com- 
municate with  the  wrist-joint. 

The  fascia  of  the  metacarpus  consists  of  a  thin  fibrous  layer 
continued  from  the  posterior  annular  ligament.  It  separates 
the  extensor  tendons  from  the  subcutaneous  veins  and  nerves, 
and  is  attached  to  the  radial  side  of  the  second  metacarpal  bone, 
and  the  ulnar  side  of  the  fifth. 

Dissection.  — The  fascia  must  be  removed  from  the  muscles, 
without  injuring  the  muscular  fibres  which  arise  from  its  under 
surface.     Preserve  the  posterior  annular  ligament. 

Superficial  Muscles  on  the  Back  of  the  Forearm.  — 
The  following  superficial  muscles  are  now  exposed,  and  should 
be  examined  in  the  order  in  which  they  are  placed,  proceeding 
from  the  radial  to  the  ulnar  side  :  i.  The  brachio- radialis  already 
described  (p.  347).  2.  The  extensor  carpi  radialis  longior. 
3.  The  extensor  carpi  radialis  brevior.  4.  The  extensor  com- 
munis digitorum.  5.  The  extensor  minimi  digiti.  6.  The 
extensor  carpi  ulnaris.     7.  The  anconeus. 

A  little  below  the  middle  of  the  forearm,  the  extensors  of  the 
wrist  and  fingers  diverge  from  each  other,  leaving  an  interval, 
in  which  are  seen  the  three  extensors  of  the  thumb  —  namely, 
the  extensor  ossis  metacarpi  pollicis,  the  extensor  brevis  pollicis, 


SUPERFICIAL    EXTENSORS    OF    THE    FOREARM. 


389 


and  the  extensor  longus  pollicis.     The  two  former  cross   ob- 
liquely over  the  radial  extensors  of  the  wrist,  and  pass  over  the 


1.  Tendon  of  the  triceps. 

2.  Origin  of  the  supinator 
longus  or  brachio-radi- 
alis. 

3.  Extensor  carpi  radialis 
longior. 

4.  Insertion  of  this  muscle. 

5.  Extensor  radialis  bre- 
vior. 

6.  Insertion  of  this  muscle. 

7.  Extensor  ossis  meta- 
carpi  pollicis. 

8.  8.  Extensor  bre\'is  or 
primi  internodii  pollicis. 

9.  q.  Extensor  longus  or 
secundi  internodii  pol- 
licis. 

10,  10.  Posterior  annular 
ligament. 

11,  Extensor  communis  di- 
gitorum. 

12,  12.  Attachments  of  the 


tendons  of  this  muscle 
to  the  middle  and  distal 
phalanges  of  the  four 
fingers. 

Tendons  of  the  exten- 
sor indicis  uniting  with 
the  tendon  of  the  com- 
munis digit orum  indicis. 

14.  Tendon  of  the  exten- 
sor minimi  digiti  min- 
gling posteriorly  with 
the  tendon  of  the  com- 
munis to  the  little  finger. 

15.  Extensor  carpi  ul- 
naris. 

16.  Its  insertion  into  the 
metacarpal  bone. 

17.  Anconeus. 

18.  Flexor  carpi  ulnaris 
attached  to  the  posterior 
border  of  the  ulna  by 
the  aponeurosis. 


Fig.  145.  —  Superficial  Extensors  of  the  Forearm, 


lower  third  of  the  radius ;  the  latter  emerges  from  under  the 
radial  border  of  the   extensor  communis  digitorum,  and   then 


390  EXTENSOR    COMMUNIS    DIGITORUM. 

passes  over  the  insertions  of  the  tendons  of  the  radial  extensors 
of  the  wrist. 

Between  the  second  and  third  extensors  of  the  thumb,  we 
observe  a  part  of  the  lower  end  of  the  radius,  which  is  not 
covered  either  by  muscle  or  tendon.  This  subcutaneous  portion 
of  the  bone  is  immediately  above  the  prominent  tubercle  in  the 
middle  of  its  lower  extremity,  and,  since  it  can  be  easily  felt 
through  the  skin,  it  presents  a  convenient  place  for  examination 
in  doubtful  cases  of  fracture. 

Extensor  Carpi  Radialis  Longior.  —  This  muscle  is  partly 
covered  by  the  supinator  radii  longus.  It  arises  from  the  lower 
third  of  the  ridge  leading  to  the  external  condyle  of  the  humerus, 
and  from  the  intermuscular  septum.  It  descends  along  the 
outer  side  of  the  forearm,  and  terminates  about  the  middle,  in  a 
flat  tendon,  which  passes  beneath  the  extensor  ossis  metacarpi 
and  brevis  pollicis,  traverses  a  groove  on  the  outer  and  back  part 
of  the  radius,  lined  by  a  synovial  membrane,  and  is  inserted  into 
the  radial  side  of  the  carpal  end  of  the  metacarpal  bone  of  the 
index  finger.  Previous  to  its  insertion,  the  tendon  is  crossed  by 
the  extensor  longus  pollicis.  It  is  suppliedhy  a  branch  from  the 
musculo-spiral  nerve  (Fig.  145,  No.  3,  p.  389).  Its  actioji  is  to 
extend  the  wrist,  slightly  to  abduct  it.  When  the  wrist  is  fixed 
it  will  assist  to  flex  the  forearm. 

Extensor  Carpi  Radialis  Brevier.  —  This  muscle  arises 
from  the  external  condyle  by  the  tendon  common  to  it  and  the 
other  extensors,  from  the  intermuscular  septa,  from  the 
external  lateral  ligament  of  the  elbow-joint  and  the  aponeurosis 
covering  the  muscle.  The  muscular  fibres  terminate  near  the 
lower  third  of  the  forearm,  upon  the  under  surface  of  a  flat  ten- 
don, which  descends,  covered  by  that  of  the  extensor  carpi 
radialis  longior,  beneath  the  three  extensors  of  the  thumb.  The 
tendon  traverses  a  groove  on  the  back  of  the  radius,  on  the  same 
plane  with  that  of  the  long  radial  extensor,  but  lined  by  a  separate 
synovial  membrane,  and  is  inserted  into  the  radial  side  of  the 
base  of  the  metacarpal  bone  of  the  middle  finger.  A  bursa  is 
generally  found  between  the  tendon  and  the  bone.  Its  neive 
comes  from  the  posterior  interosseous  (Fig.  145,  No.  5,  p.  389). 
Action  similar  to  the  longior. 

Extensor  Communis  Digitorum.  —  This  muscle  arises  from 
the  common  tendon  attached  to  the  external  condyle,  from  the 
septa  between  it  and  the  contiguous  muscles,  and  from  its  strong 
facial  covering.     A  little  below  the  middle  of  the  forearm,  the 


EX'lENSOk    MINIM]    DIGITI,    AUKICULAKIS.  39I 

muscle  divides  into  three  tendons,  which  pass,  together  with  the 
extensor  indicis,  beneath  the  posterior  annular  ligament,  through 
a  groove  on  the  back  of  the  radius  lined  by  synovial  membrane. 
On  the  back  of  the  hand  the  tendons  become  broader  and  flatter, 
and  diverge  from  each  other  towards  the  metacarpal  joints  of 
the  fingers,  where  they  become  thicker  and  narrower,  and  give 
off,  on  each  side,  a  fibrous  expansion,  which  covers  the  sides  of 
the  joint.  Over  the  first  phalanx  of  the  finger,  each  tendon 
again  spreads  out,  receives  the  expanded  tendons  of  the  lumbri- 
cales  and  interossei  muscles,  and  divides  at  the  second  phalanx 
into  three  portions,  of  which  the  middle  is  inserted  into  the  upper 
end  of  the  second  phalanx  ;  the  two  lateral,  reuniting  over  the 
lower  end  of  the  second  phalanx,  are  inserted  into  the  upper  end 
of  the  third.  *  Its  nerve  comes  from  the  posterior  interosseous. 
(Fig.  145,  No.  II,  p.  389.) 

The  oblique  aponeurotic  slips  which  connect  the  tendons  on 
the  back  of  the  hand  are  subject  to  great  variety.  The  tendon  of 
the  index  finger  is  commonly  free;  it  is  situated  on  the  radial 
side  of  the  proper  indicator  tendon,  and  becomes  united  with  it 
at  the  metacarpal  joint. 

The  tendon  of  the  middle  finger  usually  receives  a  slip  from 
that  of  the  ring.  The  tendon  of  the  ring  finger  generally  sends 
a  slip  to  the  tendons  on  either  side  of  it,  and,  in  some  cases, 
entirely  furnishes  the  tendon  of  the  little  finger.  Thus  the  ring 
finger  does  not  admit  of  independent  extension.! 

The  muscle  is  not  only  a  general  extension  of  the  fingers,  but 
can  extend  some  of  the  phalanges  independently  of  the  rest : 
e.g.,  it  can  extend  the  first  phalanges  while  the  second  and 
third  are  flexed,  the  extension  of  the  second  and  third  being  per- 
formed by  the  lumbricales.  It  is  supplied  by  the  musculo- 
spiral  nerve. 

Extensor  Minimi  Digiti,  or  Auricularis. — This  long, 
slender  muscle,  situated  on  the  ulnar  side  of  the  common  ex- 
tensor, arises  from  the  common  tendon  from  the  external  con- 


*  The  extensor  tendons  are  inserted  into  the  periosteum  ;  but  the  flexor  tendons 
are  inserted  into  the  substance  of  the  bone.  This  accounts  for  the  facility  with 
whicli  the  former  will  tear  off  the  bones  in  cases  of  necrosis,  while  the  latter  will 
adhere  so  tightly  as  to  require  cutting  before  the  phalanx  can  be  removed.  It  pro 
bably  also  explains  the  great  liability  to  necrosis  which  is  so  frequently  observed  in 
cases  of  thecal  abcess. 

t  Hence,  subcutaneous  tenotomy  of  the  web  uniting  these  extensor  tendons 
greatly  facilitates  the  piano  and  flute  players,  without  impairing  the  strength  of  their 
extensile  power.  —  A.  H. 


392  ANCONEUS. 

dyle,  and  from  the  septa  between  it  and  the  contiguous  muscles. 
Its  slender  tendon  runs  separately  beneath  the  annular  liga- 
ment immediately  behind  the  joint  between  the  radius  and  ulna, 
in  a  special  sheath  lined  by  synovial  membrane.  On  emerging 
from  the  annular  ligament,  the  tendon  splits  into  two,  which  pass 
obliquely  to  the  little  finger.  At  the  first  joint  of  the  little 
finger,  the  outer  tendon  is  joined  by  that  of  the  common  ex- 
tensor, and  both  expand  upon  the  first  and  second  phalanges, 
terminating  in  the  same  manner  as  the  extensor  tendons  of  the 
other  fingers.  Its  nerve  comes  from  the  posterior  interosseous, 
from  the  musculo-spiral.  Its  action  is  similar  to  the  communis 
digitorum,   but   confined   to  this   digit.      (Fig.    145,    No.   14,  p. 

389-) 

Extensor  Carpi  Ulnaris.  —  This   muscle  arises   from    the 

common  tendon  from  the  external  condyle,  from  the  septum 
between  it  and  the  extensor  minimi  digiti,  from  the  fascia  of  the 
forearm,  and  from  the  aponeurosis  attached  to  the  posterior 
ridge  of  the  ulna  common  to  this  muscle,  the  flexor  carpi  ulnaris, 
and  the  flexor  profundis  digitorum.  The  fibres  terminate  upon 
a  strong,  broad  tendon,  which  traverses  a  distinct  groove  on  the 
back  of  the  ulna,  close  to  the  styloid  process,  and  is  inserted 
into  the  dorsal  aspect  of  the  carpal  end  of  the  fifth  metacarpal 
bone.  Below  the  styloid  process  of  the  ulna,  the  tendon  passes 
beneath  the  posterior  annular  ligament,  over  the  back  of  the 
wrist,  and  is  confined  in  a  very  strong  fibrous  canal,  which  is 
attached  to  the  back  of  the  cuneiform,  pisiform,  and  unciform 
bones,  and  is  lined  by  a  continuation  from  the  synovial  mem- 
brane in  the  groove  of  the  ulna.  The  action  of  this  muscle  is 
to  extend  the  hand,  and  adduct  the  wrist  especially  in  pronation. 
It  is  supplied  by  the  posterior  interosseous  nerve.  (Fig.  145, 
No.  15,  p.  389.) 

In  pronation  of  the  forearm  the  lower  articular  end  of  the 
ulna  projects  between  the  tendons  of  the  extensor  carpi  ulnaris 
and  the  extensor  minimi  digiti.  A  subcutaneous  bursa  is  some- 
times found  above  the  bone  in  this  situation. 

Anconeus. — This  small  triangular  muscle  is  situated  at 
the  outer  and  back  part  of  the  elbow.  It  is  covered  by  a  strong 
layer  of  fascia,  derived  from  the  tendon  of  the  triceps,  and  ap- 
pears like  a  continuation  of  that  muscle.  It  arises  by  a  tendon 
from  the  posterior  part  of  the  external  condyle  of  the  humerus, 
and  is  inserted  into  the  triangular  surface  on  the  upper  fourth  of 
the  outer  part  of  the  ulna.     Part  of  the  under  surface  of  the 


EXTENSOR    BREVIS,    OR    PRIMI    INTERNOUII    POLLICIS.        393 

muscle  is  in  contact  with  the  capsule  of  the  elbow-joint.  Its 
action  is  to  assist  in  extending  the  forearm.  Its  no-ve  comes 
from  the  musculo-spiral  (Fig.  146,  No.  3,  p.  394). 

Dissection To  expose  the  deep  layer  of  muscles  detach 

from  the  external  condyle  the  extensor  carpi  radialis  brevior, 
the  extensor  communis  digitorum,  the  e.xtensor  minimi  digiti, 
and  the  extensor  carpi  ulnaris  ;  and,  after  noticing  the  vessels 
and  nerves  which  enter  their  under  surface,  turn  them  down. 

Deep-seated   Muscles    on    the    Back    of  the  Forearm 

The  deep-seated  muscles,  with  the  posterior  interosseous  artery 
and  nerve,  must  be  dissected.  The  muscles  exposed  are  : 
I.  The  extensor  ossis  metacarpi  pollicis.  2.  Extensor  brevis 
poUicis.  3.  E.xtensor  longus  poUicis.  4.  Extensor  indicis  or 
indicator.  5.  The  supinator  radii  brevis.  They  are  all  supplied 
by  branches  from  the  posterior  interosseous  nerve. 

Extensor  Ossis  Metacarpi  Pollicis This  muscle  lies  im- 
mediately below  the  supinator  brevis,  and  arises  from  the  pos- 
terior surface  of  the  ulna  below  the  supinator  brevis,  from  the 
posterior  surface  of  the  middle  third  of  the  radius,  and  from 
the  interosseous  membrane.  The  muscle  passes  obliquely  down- 
wards and  outwards,  crosses  the  radial  extensors  of  the  wrist 
about  three  inches  {j .^  cm)  above  the  carpus,  and  terminates 
in  a  tendon,  which  passes  along  a  common  groove  with  the 
extensor  brevis  pollicis,  lined  by  synovial  membrane,  on  the 
outer  part  of  the  lower  end  of  the  radius,  and  is  inserted  into 
the  base  of  the  metacarpal  bone  of  the  thumb,  to  the  abductor 
pollicis  *  and  frequently  also  by  a  tendinous  slip  into  the  tra- 
pezium (Fig.  146,  No.  12,  p.  394).  Its  action  is  to  abduct  and 
extend  the  first  metacarpal  bone.  Its  nen'e  is  from  the  mus- 
culo-spiral through  the  posterior  interosseus. 

Extensor  Brevis,  or  Primi  Internodii  Pollicis.  —  This, 
the  smallest  of  the  deep  muscles,  arises  from  the  middle  pos- 
terior surface  of  the  radius,  below  the  preceding,  and  from  the 
interosseus  membrane.  It  descends  obliquely  in  company  with 
the  preceding  muscle,  turns  over  the  radial  extensors  of  the  wrist, 
and  terminates  upon  a  tendon  which  passes  beneath  the  an- 
nular ligament,  through  the  groove  on  the  outer  part  of  the 
radius,  and  is  inserted  into  the  radial  side  of  the  base  of  the  first 
and  second*  phalanges  of  the  thumb  (Fig.  146,  No.  13,  p.  394). 
Its  action  is  to  extend  the  first  and  second  phalanges,  and  assists 

*  Boyl.ston  Prize  Essay,  Walsh,  1S97. 


394        EXTENSOR    LONGUS,    OR    SECUNDI    INTERNODII    POLLICIS. 


1.  Tendon  of  the  triceps. 

2.  External  head  of  the  tri- 
ceps. 

3.  Anconeus. 

4.  Origin  of  supinator  longus, 
or  brachio-radialis. 

S-  Origin  of  the  extensor 
carpi  radialis  longior. 

6,  6.  Tendon  of  this  muscle 
inserted  into  the  index  met- 
acarpal. 

7,  Origin  of  the  extensor 
carpi  radialis  brevier. 

8,  8.  Tendon  of  this  muscle 
inserted  into  the  base  of 
the  metacarpal  bone  of  the 
middle  finger. 

g.  Common  tendon  of  origin 
for  the  superficial  layer  of 
muscles. 

10.  Supinator  brevis. 

1 1 .  Insertion  of  the  pronator 
radii  teres. 

12.  Extensor  ossis  metacarpi 
pollicis. 

13.  Extensor  brevis  or  primi 
intemodii  pollicis- 


^-^  ' 


t/     , 


1    '—   I 


^ 


14.  Extensor  longus,  or  se- 
cundi  inlemodii    pollicis. 

15.  Extensor  indie  is. 

16.  Tendon  of  the  muscle 
uniting  with  the  corre- 
sponding tendon  of  the  ex- 
tensor communis. 

17.  Tendon  of  the  extensor 
minimi  digiti  uniting  with 
the  corresponding  tendon 
of  the  extensor  communis. 

18.  Tendon  of  extensor  carpi 
ulnaris. 

ig.    Flexor  carpi  ulnaris. 

20.  Fibrous  arch  extending 
from  the  epitrochlea  to  the 
olecranon  process,  f  01  ming 
the  superior  origin  of  the 
flexor  carpi  ulnaris. 

21.  Posterior  annular  liga- 
ment. 

22.  Dorsal  interossii. 

23.  Abductor  minimi  digiti. 

24.  24.  Tendons  of  the  ex- 
tensor communis  digito- 
rum. 


Fig    146.  —  Deep   Extensors  op  the  Forearm. 


the  precedin;:.^  muscles  in  abduction  of  the  thumb.      Its  nerve 
is  the  posterior  interosseous  from  the  musculo- spiral. 

Extensor  Longus,  or  Secundi  Internodii  Pollicis.  —  This 
muscle  covers  part  of  the  ori<;in  of  the  preceding  muscle,  and 
arises  from  the  posterior  surface  of  the  ulna,  below  the  extensor 


SUPINATOR    RADII    BREVIS.  395 

ossis  metcarpi  pollicis,  and  from  the  interosseous  membrane. 
The  tendon  receives  fleshy  fibres  as  low  as  the  wrist,  passes 
beneath  the  annular  ligament  in  a  distinct  groove  on  the  back 
of  the  radius,  crosses  the  tendons  of  the  radial  extensors  of  the 
wrist,  proceeds  over  the  metacarpal  bone  and  the  first  phalanx 
of  the  thumb,  and  is  inserted  into  the  base  of  the  last  phalanx 
(Fig.  146,  No.  14,  p.  394). 

The  tendons  of  the  three  extensors  of  the  thumb  may  be 
easily  distinguished  in  one's  own  hand.  The  extensor  ossis 
metacarpi  and  brevis  pollicis  cross  obliquely  over  the  radial 
artery,  where  it  lies  on  the  external  lateral  ligament  of  the 
carpus;  the  extensor  longus  pollicis  crosses  the  artery  just 
before  it  sinks  into  the  palm,  between  the  first  and  second 
metacarpal  bones,  and  is  a  good  guide  to  the  vessel.  Its  action 
is  primarily  to  extend  the  second  phalanx,  secondarily  the  first 
phalanx,  and  finally  the  whole  thumb.  It  assists  in  radial  ex- 
tension of  the  hand  and  in  slight  supination. 

Its  nerve  is  the  posterior  interosseus  from  the  musculo- 
spiral. 

Extensor  Indicis,  or  Indicator. — This  muscle  arises  from 
the  posterior  surface  of  the  ulna,  below  the  extensor  longus 
pollicis,  and  slightly  from  the  interosseous  membrane.  The 
tendon  passes  beneath  the  posterior  annular  ligament,  in  the 
same  groove,  on  the  back  of  the  radius,  with  the  tendons  of 
ihe  extensor  digitorum  communis.  It  then  proceeds  over  the 
back  of  the  hand  to  the  first  phalanx  of  the  index  finger,  where 
it  is  united  to  the  ulnar  border  of  the  common  extensor  tendon. 
By  the  action  of  this  muscle  the  index  finger  can  be  extended 
independently  of  the  others  adducting  and  abducting  the 
finger  when  the  common  extensor  is  in  tension  (Fig,  146,  No. 

15.  P-  394)- 

Dissection.  —  Reflect  the  anconeus  from  its  origin  to  expose 
the  following  muscle  :  — 

Supinator  Radii  Brevis.  —  This  muscle  embraces  the 
upper  third  of  the  radius.  It  arises  from  the  external  condyle 
of  the  humerus,  from  the  external  lateral  ligament  of  the  elbow- 
joint,  from  the  orbicular  ligament  surrounding  the  head  of  the 
radius,  from  an  oblique  ridge  on  the  outer  surface  of  the  ulna 
below  the  insertion  of  the  anconeus,  by  fleshy  fibres  from  the 
triangular  excavation  below  the  lesser  sigmoid  notch  of  the  ulna, 
and  from  the  aponeurosis  covering  the  muscle.  The  muscular 
fibres   turn  over  the  neck  and  upper  part  of  the  shaft  of  the 


596 


POSTERIOR    INTEROSSEOUS    NERVE. 


radius,  and  are  inserted  into  the  upper  third  of  this  bone  as  far 
forwards  as  the  ridge  leading  from  the  tubercle  to  the  insertion 
of  the  pronator  teres.  The  muscle  is  traversed  obliquely  by  the 
posterior  interosseus  nerve,  which  sends  a 
branch  to  it,  and  its  upper  part  is  in  contact 
with  the  capsule  of  the  ell30w-joint.  It  is  a 
powerful  supinator*  of  the  forearm,  some  of 
its  fibres  acting  at  nearly  a  right  angle  to  the 
axis  of  the  radius  (Fig.  146,  No.  10,  p.  394). 
Its  nerve  is  the  posterior  interosseous  from 
the  musculo-spiral. 

Posterior  Interosseous  Artery.  —  This 
artery  comes  from  the  ulnar  by  a  common 
trunk  with  the  anterior  interosseous  and  sup- 
plies the  muscles  on  the  back  of  the  foreami. 
It  passes  between  the  oblique  ligament  and 
the  interosseous  membrane,  and  appears,  at 
the  back,  between  the  supinator  radii  brevis 
and  the  extensor  ossis  metacarpi  pollicis. 
After  supplying  branches  to  all  the  muscles 
in  this  situation,  the  artery  descends,  much 
diminished  in  size,  between  the  superficial  and 
deep  layer  of  muscles  to  the  wrist,  where  it 
inosculates  with  the  carpal  branches  of  the 
anterior  interosseous  and  the  posterior  carpal 
branches  of  the  radial  and  ulnar  arteries. 


Fig.  147.  —  Diagram 
Showing  the  Anas- 
tomoses of  Arteries 
AT  THE  Back  op  the 
Elbow  and  Wkist 
Joints. 

I.  The  superior  pro- 
funda. 2.  Tlieanasto- 
motica  ma^na.  3.  The 
posterior  uhiar  recur- 
rent. 4.  The  poste- 
rior interosseous,  its 
ascending  and  descend- 
ing branches.  5.  The 
termination  of  the  an- 
terior interosseous.  6 
The  posterior  carpal 
arch. 

brevis,  and  descends, 


The  largest  branch  of  tliis  artery  is  the  iiiierosseoiis  re- 
current. It  ascends  beneath  the  supinator  brevis  and  the 
anconeous  to  the  space  between  the  external  condyle  and 
the  olecranon,  where  it  inosculates  with  the  branch  of  the 
superior  profunda,  which  descends  in  the  substance  of  the 
triceps,  with  the  posterior  ulnar  recurrent  artery,  and  with 
the  anastomotica  magna. 

In  the  lower  part  of  the  back  of  the  forearm  a  branch 
of  the  anterior  interosseous  arteiy  is  seen  passing  through 
the  interosseous  membrane  to  reach  the  back  of  the  wri.st. 

Posterior  Interosseous  Nerve.  —  The  nerve  which 
supplies  the  muscles  on  the  back  of  the  forearm  is  the  pos- 
terior interosseous,  one  of  the  divisions  of  the  musculo- 
spiral.  It  passes  obliquely  through  the  supinator  radii 
lying  on  the  lower  fibres  of  this  muscle,  the  extensoies  ossis 

*  As  the  muscle  is  able  to  turn  the  radius  nearly  180  degrees,  great  care  should 
be  taken  in  fracture  of  the  upper  third  of  this  bone  to  place  the  lower  fragment  in 
extreme  supination  to  preserve  the  pronating  and  supinating  function  of  the  fore- 
arm. Especially  is  it  to  be  remembered  that  the  biceps  as.sist  in  supination,  and 
all  antagonizing  force  is  removed  in  this  fracture.  —  A.  H. 


RADIAL    ARTERY    ON    THE    BACK    OF    THE    WRIST.  39/ 

metacarpi  and  brevis  pollicis,  and  beneath  the  superficial  extensors.  It  then,  much 
diminished  in  size,  passes  under  the  extensor  longus  pollicis,  on  the  interosseous 
membrane,  as  far  as  the  posterior  annular  ligament,  where  it  presents  a  gangliform 
enlargement.  Between  the  supeificial  and  deep  layer  of  muscles  it  sends  to  each 
a  filament,  generally  in  company  with  a  branch  of  the  posterior  interosseous  artery. 
It  sends  a  branch  to  the  extensor  carpi  radialis  brevior,  and  supplies  the  supinator 
brevis  in  passing  through  its  substance.  The  brachio-radialis  and  the  extensor 
carpi  radialis  longior  are  supplied  by  distinct  branches  from  the  musculo-spiral 
nerve. 

After  the  posterior  interosseous  nerve  descends  beneath  the  extensor  longus 
pollicis,  it  lies  on  the  interosseous  membrane,  beneath  the  extensor  digitorum 
communis  and  the  indicator.  At  the  back  of  the  wrist,  beneath  the  annular  liga- 
ment, it  forms  the  gangliform  enlargement  from  which  filaments  are  sent  to  the 
carpal  and  metacarpal  joints. 

Dissection.      Radial  Artery  on  the   Back  of  the  Wrist. 

—  The  radial  artery  is  continued  over  the  external  lateral  liga- 
ment of  the  carpus,  beneath  some  filaments  of  the  radial  nerve, 
cutaneous  veins,  and  the  extensor  tendons  of  the  thumb,  to  the 
proximal  part  of  the  interval  between  the  first  and  second  meta- 
carpal bones,  where  it  dips  down  between  the  two  origins  of  the 
abductor  indicis,  and,  entering  the  palm,  forms  the  deep  palmar 
arch.  In  this  part  of  its  course  it  is  accompanied  by  a  filament 
of  the  musculo-cutaneous  nerve ;  observe  also  that  the  tendon 
of  the  extensor  longus  pollicis  passes  over  it  immediately  before 
it  sinks  into  the  palm.  It  supplies  in  this  part  of  its  course  the 
following  small  branches  to  the  back  of  the  hand :  — 

a.  Posterior  carpal  artery. — This  branch  passes  across  the  carpal  bones  be- 
neath the  extensor  tendons.  It  inosculates  with  the  termination  of  the  anterior 
interosseous  artery,  and  forms  an  arch  beneath  the  extensor  tendons,  with  a  corre- 
sponding branch  from  the  ulnar  artery.  The  carpal  arch  sends  off  small  branches, 
called  the  dorsal  interosseous,  which  descend  along  the  third  and  fourth  interosse- 
ous spaces  from  the  arch  just  mentioned,  beneath  the  extensor  tendons,  and  inos- 
culate near  the  carpal  ends  of  the  metacarpal  bones  with  the  perforating  branches 
from  the  deep  palmar  arch. 

b.  Thejirst  dorsal  interosseous  artery  is  generally  larger  than  the  others.  It 
passes  forwards,  beneath  the  extensors  of  the  thumb,  on  the  second  interosseous 
space  to  the  cleft  between  the  index  and  middle  fingers,  communicating  here  with 
a  perforating  branch  of  the  deep  palmar  arch,  and  terminates  in  small  bianches, 
some  of  which  proceed  along  the  back  of  the  fingers,  others  inosculate  with  the 
palmar  digital  arteries. 

c.  The  dorsalis  indicis,  a  branch  of  variable  size,  passes  over  the  first  inter- 
osseous muscle  along  the  radial  side  of  the  back  of  the  index  finger. 

d.  The  dorsales  pollicis  are  two  small  branches  which  arise  from  the  radial 
opposite  the  head  of  the  first  metacarpal  bone,  and  run  along  the  back  of  the 
thumb,  one  on  either  side.     They  are  often  absent. 

These  dorsal  interosseous  arteries  supply  the  extensor  tendons  and  their 
sheaths,  the  interosseous  muscles,  and  the  skin  on  the  back  of  the  hand  and  the 
first  phalanges  of  the  fingers. 

Dissection Remove  the  tendons  from  the  back  and  from 

the  palm  of  the  hand;  observe  the  deep  palmar  fascia  which 


398  DORSAL    ]NTEROSSEI. 

covers  the  interosseous  muscles.  It  is  attached  to  the  ridges 
of  the  metacarpal  bones,  forms  a  distinct  sheath  for  each  inter- 
osseous muscle,  and  is  continuous  inferiorly  with  the  transverse 
metacarpal  ligament.  On  the  back  of  the  hand  the  interosseous 
muscles  are  covered  by  a  thin  fascia,  which  is  attached  to  the 
adjacent  borders  of  the  metacarpal  bones. 

Transverse  Metacarpal  Ligament.  —  This  consists  of 
strong  bands  of  ligamentous  fibres,  which  pass  transversely  be- 
tween the  distal  extremities  of  the  metacarpal  bones.  These 
bands  are  intimately  united  to  the  fibro-cartilaginous  ligament 
of  the  metacarpal  joints,  and  are  of  sufificient  length  to  admit  of 
a  certain  degree  of  movement  between  the  ends  of  the  metacar- 
pal bones. 

Dissection Remove  the  fascia  which  covers  the  inter- 
osseous muscles,  and  separate  the  metacarpal  bones  by  dividing 
the  transverse  metacarpal  ligament.  A  biusa  is  frequently 
developed  between  their  digital  extremities. 

Interosseous  Muscles. — These  muscles,  so  named  from 
their  position,  extend  from  the  sides  of  the  metacarpal  bones  to 
the  bases  of  the  first  phalanges  and  the  extensor  tendons  of  the 
fingers.  In  each  interosseous  space  (except  the  first,  in  which 
there  is  only  an  abductor)  there  are  two  muscles,  one  of  which 
is  an  abductor,  the  other  an  adductor,  of  a  finger.  Thus  there 
are  seven  in  all,  four  of  which,  situated  on  the  back  of  the  hand, 
are  called  dorsal;  the  remainder,  seen  only  in  the  palm,  are 
called  palmar.*     They  are  all  supplied  by  the  ulnar  nerve. 

Dorsal  Interossei.  —  Each  dorsal  interosseous  is  a  bipenni- 
form  muscle,  and  arises  from  the  opposite  sides  of  two  contigu- 
ous metacarpal  bones  (Figs.  148  and  149).  From  this  double 
origin  the  filores  converge  to  a  tendon,  which  passes  between 
the  metacarpal  joints  of  the  finger,  and  is  ijiserti d  m\o  the  side 
of  the  base  of  the  first  phalanx,  and  by  a  broad  expansion  into 
the  extensor  tendon  on  the  back  of  the  same  finger. 

The.  first  dorsal  ititerosseous  muscle  (abdjtclor  indicis)  is  larger 
than  the  others,  and  occupies  the  interval  between  the  thumb 
and  forefinger.  It  arises  from  the  proximal  half  of  the  ulnar 
side  of  the  first  metacarpal  bone,  and  from  the  entire  length  of 
the  radial  side  of  the  .second  :  between  the  two  origins,  the 
radial  artery  passes  into  the  palm.      Its  fibres  converge  on  either 

*  If  we  consider  the  adductor  pollicis  as  a  palmar  interosseous  muscle,  there 
would  be  four  palmar  and  four  dorsal  —  all  supplied  by  the  ulnar  nerve. 


PALMAR    INTEROSSEOUS. 


399 


side  to  a  tendon,  which  is  msertcd  into  the  radial  side  of  the 
first  phalanx  of  the  index  finger,  and  its  extensor  tendon. 

The  second  dorsal  interosseous  muscle  occupies  the  second 
metacarpal  space.  It  is  inserted  into  the  radial  side  of  the 
first  phalanx  of  the  middle  finger  and  its  extensor  tendon. 

The  third  ?iX\d  fo7irth,  occupying  the  corresponding  metacarpal 
spaces,  are  inserted,  the  one  into  the  ulnar  side  of  the  middle,  the 
other  into  the  ulnar  side  of  the  ring  finger  (Fig.  146,  No.  22, 

P-  394)- 

If  a  line  be  drawn  longitudinally  through  the  middle  finger, 
as  represented  by  the  dotted  line  in  Fig.  149,  we  find  that  all 


Fig.  148.  —  Diagram  of  the  Four  Dorsal 
Intekossei,  Drawing  from  the  Mid- 
dle Line. 


Fig.  149.  —  Diagram  of  the  Three  Pal- 
mar Interossei,  and  the  Adductor 
PoLLicis,  Drawing  Towards  the  Mid- 
dle Line. 


the  dorsal  interosseous  muscles  are  abductors  from  that  line  ; 
consequently  they  separate  the  fingers  from  each  other. 

Palmar  Interosseous.  —  It  requires  a  careful  examination  to 
distinguish  this  set  of  muscles,  because  the  dorsal  muscles  pro- 
trude with  them  into  the  palm.  They  are  smaller  than  the 
dorsal,  and  each  arises  from  the  lateral  surface  of  only  one  meta- 
carpal bone  —  that,  namely,  connected  with  the  finger  into  which 
the  muscle  is  inserted  (Fig.  149).  They  terminate  in  small  ten- 
dons, which  pass  between  the  metacarpal  joints  of  the  fingers, 
and  are  inserted,  like  those  of  the  dorsal  muscles,  into  the  sides 
of  the  first  phalanges  and  the  extensor  tendons  on  the  back  of 
the  fingers. 


400  DISSECTION    OF    THE    LIGAMENTS. 

'Y\\Q.  first  palmar  interosseous  muscle  arises  from  the  ulnar  side 
of  the  second  metacarpal  bone,  and  is  inserted  into  the  ulnar 
side  of  the  index  finger.  The  second  and  tJiird  arise,  the  one 
from  the  radial  side  of  the  fourth,  the  other  from  the  radial  side 
of  the  fifth  metacarpal  bone,  and  are  inserted  into  the  same  sides 
of  the  ring  and  little  fingers. 

The  palmar  interosseous  muscles  are  all  adductors  to  a  line 
drawn  through  the  middle  finger  (Fig.  149).  They  are,  there- 
fore, the  opponents  of  the  dorsal  interosseous,  and  move  the 
fingers  towards   each  other.* 

The  palmar  and  dorsal  interossei  are  supplied  by  filaments 
from  the  deep  branch  of  the  ulnar  nerve  (Fig.  131,  No.  -^6, 
P-  337)- 

DISSECTION    OF   THE    LIGAMENTS. 

Sterno-clavicular  Joint.  —  The  inner  end  of  the  clavicle  ar- 
ticulates with  the  comparatively  small  and  shallow  excavation  on 
the  upper  and  outer  part  of  the  sternum,  and  is  an  arthrodial 
joint.  The  security  of  the  joint  depends  upon  the  great  strength 
of  its  ligaments.  There  are  two  synovial  membranes,  and  an 
intervening  fibro-cartilage. 

The  anterior  stemo-clavicular  ligament  (Fig.  1 50)  consists 
of  a  lax,  strong,  broad  band  of  ligamentous  fibres,  which  pass 
obliquely  downwards  and  inwards  over  the  front  of  the  joint, 
from  the  inner  end  of  the  clavicle  to  the  anterior  surface  of  the 
sternum. 

*  The  interossei,  probably,  also  assist  the  flexors  of  the  fingers  when  the  latter 
are  slightly  flexed  at  their  metacarpophalangeal  joints.  M.  Duchenne  believes 
that,  in  addition  to  their  usually  ascribed  function  of  abduction,  adduction,  and 
supplemental  flexion  at  the  metacarpo-phalangeal  articulation,  the  interossei  act 
as  extensors  of  the  second  and  third  phalanges ;  the  common  extensor  tendons 
acting  only  as  extensors  of  the  first  phalanges.  {Physiologic  des  Mouvefne?ils,  etc., 
1867).  The  action  of  the  lumbricales  in  extending  the  second  and  third  phalanges 
(even  if  they  are  not  the  chief  factors  of  this  movement)  must  not  be  lost  sight  of, 
for  in  a  case,  recorded  in  St.  Bartholomew" s  Hospital  Reports,  1881,  in  which  the 
ulnar  nerve  had  been  divided  a  short  distance  above  the  wrist-joint,  the  first 
phalanges  of  the  ring  and  httle  fingers  were  bent  (extended)  upon  their  articu- 
lating metacarpal  bones,  the  second  and  third  phalanges  being  flexed  at  obtuse 
angles  upon  their  proximal  phalanges ;  the  index  and  middle  fingers  being  normal. 
I  attribute  this  condition  to  paralysis  of  the  two  ulnar  lumbricales  and  not  to  loss 
of  power  of  the  interossei.  I  have  seen  about  a  dozen  instances  of  division  of  the 
ulnar  nerve,  and  in  all  of  them  the  same  condition  of  the  little  and  ring  fingers 
has  existed. 

[The  common  action  of  the  interossei  is  to  flex  the  first  and  extend  the  second 
and  third  phalanges.  — A.  H  J 


DISSKCTION    OF    THE    LIGAMENTS. 


401 


The  posterior  sterno-clavicular  ligament,  stronger  and  denser 
than  the  anterior,  extends  over  the  back  of  the  joint,  its 
fibres  passing  downwards  and  inwards  from  the  back  of  the 
clavicle  to  the  back  of  the  sternum  in  a  similar  manner  of  the 
anterior. 

The  interclavicular  ligament  connects  the  clavicles  directly. 
It  extends  transversely  along  the  notch  of  the  sternum,  and  has 
a  broad  attachment  to  the  upper  border  of  each  clavicle.  Be- 
tween the  clavicles  it  is  more  or  less  attached  to  the  sternum, 
so  that  it  forms  a  curve  with  the  concavity  upwards. 

The  three  ligaments  just  described  are  so  closely  connected 
that,  collectively,  they  form  for  the  joint  a  complete  fibrous 
capsule  of  such  strength  that  dislocation  of  it  is  rare. 


Fig   150.  —  Diagram  of  the  Sterno-clavicular  Ligaments. 


I.    Interclavicular    ligament      2.   Anterior    sterno-clavicular    ligament.      3.   Costo-clavicular   liga- 
ment     4.  Interarticular  fibro-cartilage 


The  costo-clavicular  or  rhomboid  ligament  connects,  the  clavicle 
to  the  cartilage  of  the  first  rib.  It  ascends  obliquely  outwards 
and  backwards  from  the  cartilage  of  the  rib  to  a  rough  surface 
beneath  the  sternal  end  of  the  clavicle.  Its  use  is  to  limit  the 
elevation  of  the  clavicle.  There  is  such  constant  movement 
between  the  clavicle  and  the  cartilage  of  the  first  rib  that  a  well- 
marked  bu7'sa  is  commonly  found  between  them. 

Interarticular  fibro-cartilage.  To  see  this,  cut  through  the 
rhomboid,  the  anterior  and  posterior  ligaments  of  the  joint,  and 
raise  the  clavicle.  It  is  nearly  circular  in  form,  and  thicker  at 
the  circumference  than  the  centre,  in  which  there  is  sometimes 
a  perforation,  and  divides  the  articulation  into  two  cavities.  In- 
feriorly,  it  is  attached  to  the  cartilage  of  the  first  rib,  close  to  the 
sternum  ;  superiorly,  to  the  upper  part  of  the  clavicle  and  the 


402  SCALPO-CLAVICULAR    JOINT, 

interclavicular  ligament.  Its  circumference  is  inseparably  con- 
nected with  the  anterior  and  posterior  ligaments.* 

The  joint  is  provided  with  two  synovial  membranes :  one  be- 
tween the  articular  surface  of  the  sternum  and  the  inner  surface 
of  the  fibro-cartilage ;  the  other  between  the  articular  surface  of 
the  clavicle  and  the  outer  surface  of  the  fibro-cartilage. 

This  interarticular  fibro-cartilage  is  a  structure  highly  elastic, 
without  admitting  of  any  stretching.  It  equalizes  pressure,  breaks 
shocks,  and  also  acts  as  a  ligament,  tending  to  prevent  the  clavi- 
cle from  being  driven  inwards  towards  the  mesial  line. 

Observe  the  relative  form  of  the  cartilaginous  surfaces  of  the 
bones  :  that  of  the  sternum  is  slightly  concave  in  the  transverse, 
and  convex  in  the  antero-posterior  direction  ;  that  of  the  clavicle 
is  the  reverse. 

The  form  of  the  articular  surfaces  and  the  ligaments  of  a  joint 
being  known,  it  is  easy  to  understand  the  movements  of  which  it 
is  capable.  The  clavicle  can  be  moved  upon  the  sternum  in  a 
direction  either  upwards,  downwards,  backwards,  or  forwards  ; 
it  also  admits  of  circumduction.  These  movements,  though 
limited  at  the  sternum,  are  considerable  at  the  apex  of  the 
shoulder.f 

Scalpo-clavicular  Joint.  —  The  outer  end  of  the  clavicle 
articulates  with  the  acromion,  and  is  connected  by  strong  liga- 
ments to  the  coracoid  process  of  the  scapula. 

The  clavicle  and  the  acromion  articulate  with  each  other  by 
two  flat  oval  cartilaginous  surfaces,  of  which  the  planes  slant 
inwards,  and  the  longer  diameters  are  in  the  antero-posterior 
direction.     It  is  an  arthrodial  joint. 

The  superior  acromio-clavicular  ligament,  a   broad  band  of 

*  Interarticular  fibro-cartilages  (menisci)  also  exist  in  the  following  joints: 
acromio-clavicular,  temporomandibular,  knee,  and  wrist  joints.  Professor  Hum- 
phry has  shown  that  interarticular  cartilages  augment  the  variety  of  movements 
in  a  joint,  permitting  for  instame  that  of  rotation  in  the  knee-joint,  in  addition  to 
that  of  extension  and  flexion,  which  otherwise  would  be  the  only  possible  ones. 

t  Professor  Humphi-y,  in  describing  the  movements  of  this  joint,  in  his  valuable 
work,  "On  the  Human  Skeleton,"  says,  "The  movements  attendant  on  elevation 
and  depression  of  the  shoulder  take  place  between  the  clavicle  and  the  inter- 
articular ligament,  the  bone  rotating  upon  the  ligament  on  an  axis  drawn  from 
before  backwards  through  its  own  articular  facet.  When  the  shoulder  is  moved 
forwards  and  backwards,  the  clavicle,  with  the  interarticular  ligament,  rolls  to  and 
fro  on  the  articular  surface  of  the  sternum,  revolving,  with  a  .slightly  sliding  move- 
ment, round  an  axis  drawn  nearly  vertically  tiirough  the  sternum  In  the  circum- 
duction of  the  shoulder,  which  is  compounded  oi  these  two  movements,  the  clavicle 
revolves  upon  the  interarticular  cartilage,  and  the  latter,  with  the  clavicle,  rolls  upon 
th^  sternqm." 


LIGAMENTS    OF    THE    SCAF'ULA. 


403 


parallel  ligamentous  fibres,  strengthened  by  the  aponeurosis  of 
the  trapezius,  extends  from  the  upper  surface  of  the  acromion 
to  the  upper  surface  of  the  clavicle. 

The  inferior  acromio-claviciilar  ligament,  of  less  strength,  ex- 
tends along  the  under  surface  of  the  joint  from  bone  to  bone.* 

An  inter  articular  Jibro-carti/agc  \s  somtUmts  found  in  this 
joint ;  but  it  is  incomplete,  and  seldom  extends  lower  than  the 
upper  half.     There  is  only  one  synovial  membrane. 

Coraco-clavicular  ligament.  The  clavicle  is  connected  to 
the  coracoid  process  of  the  scap- 
ula by  two  strong  ligaments  j- 
—  the  conoid  and  trapezoid  — 
which,  being  continuous  with 
each  other,  should  be  considered 
as  one.  The  trapezoid  ligament 
is  the  more  anterior  and  ex- 
ternal. Quadrilateral  in  shape, 
it  arises  from  the  back  of  the 
upper  surface  of  the  coracoid 
process,  and  ascends  obliquely 
backwards  and  outwards  to  the 
oblique  line  on  the  under  aspect 
of  the  clavicle,  near  its  outer 
end.  The  conoid  ligament,  tri- 
angular in  form,  is  situated  be- 
hind the  trapezoid  ligament  to 
the  posterior  border  of  which  it 
is  attached.  It  is  fixed  at  its  apex  to  the  root  of  the  coracoid 
process,  ascends  nearly  vertically,  and  is  attached  by  its  base  to 
the  clavicle.  The  coraco-clavicular  ligaments  fix  the  scapula 
to  the  clavicle,  and  prevent  undue  rotation  of  the  scapula. 
When  the  clavicle  is  fractured  in  the  line  of  the  attachment  of 
the  coraco-clavicular  ligament,  there  is  little  or  no  displace- 
ment of  the  fractured  ends,  these  being  kept  in  place  by  the 
ligament. 

Ligaments  of  the  Scapula.  —  These  are  three  :  the  coraco- 
acromial  or  triangular  ligament,  attached  by  its  apex  to  the  tip 


Fig.  151.  — Anterior  View  of  the  Scapulo- 
clavicular Ligaments,  and  of  the 
Shoulder-Joint. 

I.  Trapezoid  portions  of  the  coraco-clavicular 
ligament.  2.  Conoid  portions  of  the  coraco- 
clavicular  li,gament.  3.  Suprascapular  or 
transverse  li,c;ament.  4-  Coraco-acromial  liga- 
ment. 5.  Tendon  of  biceps.  6.  Capsular 
ligament  of  the  shoulder -joint.  7.  Coraco- 
humeral  ligament.  8.  Foramen  in  the  capsu- 
lar ligament  for  the  subscapularis  tendon. 


*  The  superior  and  inferior  ligaments  practically  make  a  capsular  ligament,  and 
are  described  as  such  by  some  authors. 

t  This  is  a  union  and  not  a  joint  proper,  as  it  is  but  rarely  that  the  bones  are 
found  in  contact,  and  when  this  does  take  place  articular  cartilage  covers  their 
union,  and  a  synovial  membrane  is  present.  —  A.  H. 


404  SHOULDER-JOINT. 

of  the  acromion  process,  and  by  its  base  to  the  outer  border 
of  the  coracoid  process  ;  it  is  separated  from  the  upper  part  of 
the  capsule  of  the  shoulder-joint  by  a  large  bursa ;  and  the 
transverse  or  coracoid  ligament,  which  passes  across  the  supra- 
scapular notch,  converting  it  into  a  foramen.  The  inferior 
transverse  or  spino-glcnoid  ligament  is  attached  to  the  external 
margin  of  the  spine  of  the  scapula  immediately  above  the 
glenoid  cavity,  and  extends  in  an  oblique  direction  to  the  upper 
and  posterior  margin  of  the  glenoid  cavity.  It  makes  a  fora- 
men for  the  suprascapular  vessels  and  nerve  to  gain  the  infra- 
spinous  fossa,  and  protects  these  structures  from  pressure.  - — 
A.  H.  The  suprascapular  vessels  pass  over  the  foramen,  the 
suprascapular  nerve  through  it. 

Shoulder-joint.  —  The  articular  surface  of  the  head  of  the 
humerus,  forming  rather  more  than  one-third  of  a  sphere,  moves 
upon  the  shallow  glenoid  cavity  of  the  scapula,  which  is  of  an 
almond  shape,  with  the  broader  end  downwards  and  the  long 
diameter  nearly  vertical.  The  security  of  the  joint  depends  not 
upon  any  mechanical  contrivance  of  the  bones,  but  upon  the 
great  strength  and  number  of  the  ligaments  and  tendons  which 
surround  and  are  intimately  connected  with  it.  It  is  an  enar- 
throdial,  or  ball-and-socket  joint. 

To  admit  the  free  motion  of  the  head  of  the  humerus  upon 
the  glenoid  cavity  it  is  requisite  that  the  capsular  ligament  of 
the  joint  be  loose  and  capacious.  Accordingly,  the  head  of  the 
bone,  when  detached  from  its  muscular  connections,  may  be 
separated  from  the  glenoid  cavity  to  the  extent  of  an  inch  {2.^ 
cm.)  or  more,  without  laceration  of  the  capsule.  This  explains 
the  elongation  of  the  arm  observed  in  some  cases  in  which 
effusion  takes  place  into  the  joint ;  also  in  cases  of  paralysis  of 
the  deltoid. 

The  capsular  ligament  is  attached  above,  round  the  circum- 
ference of  the  glenoid  cavity  ;  below,  round  the  anatomical  neck 
of  the  humerus.  It  is  strongest  on  its  upper  aspect,  weakest 
and  longest  on  its  lower.  It  is  strengthened  on  its  upper  and 
posterior  part  by  the  tendons  of  the  supraspinatus,  infraspina- 
tus, and  teres  minor ;  *  its  inner  part  is  strengthened  by  the 
broad  tendon  of  the  subscapulars  and  the  coraco-humeral 
ligament  ;  its  lower  part  by  the  long  head  of  the  triceps. 

*  Occasionally  these  tendons  enter  the  capsule  as  the  tendon  of  the  biceps 
muscle  forming  processes  from  the  subacromial  bursa.  —  A.  H. 


SHOULDER-JOINT.  4O5 

Thus  the  circumference  of  the  capsule  is  surrounded  by  ten- 
dons on  every  side,  excepting  a  small  space  towards  the  axilla. 
If  the  humerus  be  raised,  it  will  be  found  that  the  head  of  the 
bone  rests  upon  this  unprotected  portion  of  the  capsule,  be- 
tween the  tendons  of  the  subscapularis  and  the  long  head  of 
the  triceps  ;  through  this  part  of  the  capsule  the  head  of  the 
bone  is  first  protruded  in  dislocations  into  the  axilla. 

At  the  upper  and  inner  side  of  the  joint,  a  small  opening  is 
observable  in  the  capsular  ligament,  through  which  the  tendon 
of  the  subscapularis  passes,  so  that  the  synovial  membrane  of 
the  joint  communicates  with  the  bursa  under  the  tendon  of  this 
muscle.  A  second  opening  exists  in  the  lower  part  of  the  front 
of  the  capsular  ligament,  where  the  tendon  of  the  biceps  emerges 
from  the  joint.  A  third  opening  occasionally  exists  between 
the  joint  and  a  bursa  under  the  tendon  of  the  infraspinatus 
muscle. 

The  upper  and  inner  surface  of  the  capsule  is  strengthened 
by  a  strong  band  of  ligamentous  fibres,  called  the  coraco-Jiumeral 
or  accessory  ligament.  It  is  attached  to  the  root  of  the  cora- 
coid  process,  and  extending  to  the  tip,  expands  over  the  upper 
surface  of  the  capsule,  with  which  it  is  inseparably  united,  and, 
passing  downwards  and  outwards,  is  attached  to  the  greater 
tuberosity  of  the  humerus. 

Open  the  capsule  to  see  the  tendon  of  the  long  head  of  the 
biceps.  It  arises  by  a  rounded  tendon  from  the  upper  margin 
of  the  glenoid  cavity,  and  is  continuous  with  the  glenoid  liga- 
ment ;  becoming  slightly  flattened,  it  passes  over  the  head  of 
the  humerus,  descends  through  the  groove  between  the  two 
tuberosities,  and,  after  piercing  the  capsular  ligament  of  the 
shoulder-joint,  it  passes  along  the  bicipital  groove,  being  retained 
in  situ  by  an  aponeurotic  prolongation  from  the  tendon  of  the 
pectoralis  major.  It  is  loose  and  movable  within  the  joint.  It 
acts  like  a  strap,  keeping  down  the  head  of  the  bone  when  the 
arm  is  raised  by  the  deltoid,  and  then  might  be  considered 
as  taking  the  part  of  a  ligament  of  the  joint. 

The  tendon  of  the  biceps,  strictly  speaking,  does  not  perfo- 
rate the  synovial  membrane  of  the  joint.  It  is  enclosed  in  a 
tubular  sheath,  which  is  reflected  over  it  at  its  attachment  to 
the  glenoid  cavity,  and  accompanies  it  for  two  inches  (5  cm.) 
down  the  groove  of  the  humerus. 

The  gleno-hunieral  ligament  is  attached  to  the  base  of  the 
coracoid  process,  is  internal  to  the  capsule  and  the  margin  of 


406  SHOULDER-JOINT. 

the  glenoid  cavity,  and  runs  to  the  lesser  tuberosity  of  the  hu- 
merus. It  is  attached  to  the  capsule  and  meets  the  tendon  of 
the  biceps  at  an  acute  angle.*  There  are  two  other  processes, 
less  marked  ;  one  connecting  the  glenoid  cavity  and  lesser  tuber- 
osity, derived  from  the  subscapularis  tendon;  the  other  from 
the  inferior  part  of  the  glenoid  cavity  to  the  inferior  part  of  neck 
of  the  humerus.     This  ligament  is  best  seen  in  the  foetal  state. 

The  margin  of  the  glenoid  cavity  of  the  scapula  is  surrounded 
by  a  fibro-cartilaginous  band  of  considerable  thickness,  called 
Xh^  glenoid  ligament.  This  not  only  enlarges,  but  deepens  the 
cavity.  Superiorly,  it  is  continuous  on  either  side  with  the  ten- 
don of  the  biceps ;  inferiorly,  with  the  tendon  of  the  triceps  ; 
in  the  rest  of  its  circumference  it  is  attached  to  the  edge  of  the 
cavity. 

The  cartilage  covering  the  head  of  the  humerus  is  thicker  at 
the  centre  than  at  the  circumference.  The  reverse  is  the  case 
in  the  glenoid  cavity. 

The  synovial  membrane  lining  the  under  surface  of  the  cap- 
sule is  reflected  around  the  tendon  of  the  biceps,  and  passes 
with  it  in  the  form  of  a  cul-de-sac  down  the  bicipital  groove. 
On  the  inner  side  of  the  joint  it  always  communicates  with  the 
bursa  beneath  the  tendon  of  the  subscapularis. 

There  is  also  a  large  bursa  situated  between  the  capsule  and 
the  deltoid  muscle,  which  does  not  communicate  with  the  joint. 

The  muscles  in  relation  with  the  joint  are  :  above,  the  supra- 
spinatus  ;  behind,  the  infraspinatus  and  teres  minor  ;  below, 
the  long  head  of  the  triceps  ;  internally,  the  subscapularis  ;  and, 
inside  the  joint,  the  long  head  of  the  biceps. 

The  shoulder-joint  is  an  enarthrodial  joint,  and  has  a  more 
extensive  range  of  motion  than  any  other  joint  in  the  body  ;  it 
is  what  mechanics  call  a  universal  joint.  It  is  capable  of  mo- 
tion forwards  and  backwards,  of  adduction,  abduction,  circum- 
duction, and  rotation.  The  various  movements  are  limited 
chiefly  by  the  surrounding  muscles  and  by  atmospheric  pressure, 
for  the  capsule  is  so  lax  as  to  offer  no  obstacle  to  the  freedom 
of  movement  in  any  direction.  The  amount  of  rotation  which 
the  head  of  the  humerus  is  capable  of,  is  to  the  extent  of  a 
quarter  of  a  circle. 

The  movements  of  which  the  shoulder-joint  is  capable  are 
efiFected  by  the  following  muscles,  thus  :  — 

*  Morris's  Anatomy,  1898. 


ELBOW-JOINT. 


407 


Extension  is  effected  by  the  posterior  fibres  of  the  deltoid, 
latissimus  dorsi,  teres  major,  and  (when  the  arm  is  raised)  by 
the  infraspinatus  and  teres  minor. 

Flexion,  by  the  anterior  fibres  of  the  deltoid,  coraco-brachialis, 
and  the  pectoralis  major  (slightly). 

Abduction,  by  the  deltoid  and  the  supraspinatus. 

Adduction,  by  the  pectoralis  major,  latissimus  dorsi,  teres 
major,  coraco-brachialis,  and  (when  the  arm  is  raised)  by  the 
subscapularis. 

Rotation  imvards,  by  the  subscapularis,  latissimus  dorsi,  and 
teres  major. 

Rotation  oiitivards,  by  the  infraspinatus  and  the  teres  minor.* 

Elbow-joint.  — The  elbow-joint  is  a  ginglymus  or  hinge- 
joint.  The  larger  sigmoid  cavity  of  the  ulna  is  adapted  to  the 
trochlea  upon  the  lower  end  of  the  hu- 
merus, admitting  only  of  flexion  and  ex- 
tension ;  while  the  shallow  excavation  upon 
the  head  of  the  radius  admits  not  only  of 
free  flexion  and  extension,  but  of  central 
rotation,  upon  the  rounded  articular  emi- 
nence {capitelluni)  of  the  humerus,  and  of 
peripheral  rotation  at  the  superior  radio- 
ulnar articulation. 

The  joint  is  secured  in  front  and  behind 
by  anterior  and  posterior  ligaments,  and 
laterally  by  tivo  strong  lateral  ligaments. 
No  ligament  is  attached  to  the  head  of 
the  radius,  otherwise  its  rotary  movement 
would  be  impeded.  The  head  is  simply 
surrounded  by  a  ligamentous  collar,  called 
the  annular  ligament,  within  which  it  freely 
rolls  in  pronation  and  supination  of  the 
hand. 

The  anterior  ligament  consists  of  broad, 
thin  inverted  V-shaped  ligamentous  fibres, 
attached  above  to  the  front  of  the  hu- 
merus, above  the  coronoid  fossa,  below  to  the  coronoid  pro- 
cess of  the  ulna  and  to  the  orbicular  ligament,  and  continuous 
on  each  side  with  the  lateral  ligaments. 

*  With  the  humerus  vertical  the  supraspinatus  will  act  as  an  external  rotator. 
It  should  also  be  borne  in  mind  that  the  joint  depends  more  for  its  strength  upon 
the  muscles  and  their  tendons  which  surround  it  than  upon  the  ligaments.  —  A.H. 


.  —  Ligaments  of  the 

Elbow- Joint. 

External  lateral  lieament. 
b.  Orbicular  or  annular  liga- 
ment, c.  Part  of  internal 
lateral  ligament,  d.  Radius, 
removed  from  the  anr.ular 
ligament. 


40S  SUPERIOR    RADIO-ULNAR    ARTICULATION. 

T\\Q.  posterior  liganioit  is  composed  of  thin,  loose,  inverted  V- 
shaped  fibres  attached  above  to  the  margin  of  the  olecranon 
fossa,  below  to  the  border  of  the  olecranon,  and  spread  over 
the  posterior  aspect  of  the  joint. 

The  internal  lateral  ligament  is  thick,  tense,  strong  and  tri- 
angular, and  is  divided  into  two  portions,  an  anterior  and  a  pos- 
terior. Its  anterior  part  is  attached  to  the  front  of  the  internal 
condyle  of  the  humerus  ;  from  this  point  the  fibres  radiate,  and 
are  inserted  along  the  inner  margin  of  the  coronoid  process  of 
the  ulna.  Tht  posterior  part  is  also  triangular,  and  passes  from 
the  back  part  of  the  internal  condyle  to  the  inner  border  of  the 
olecranon. 

A  band  of  fibres  extends  transversely  from  the  olecranon  to 
the  coronoid  process,  across  a  notch  observable  on  the  inner 
side  of  the  sigmoid  cavity  ;  through  this  notch  small  vessels  pass 
into  the  joint. 

The  external  lateral  ligament,  thick,  tense  and  strong,  is  at- 
tached to  the  external  condyle  of  the  humerus,  and  is  in  intimate 
connection  with  the  common  tendon  of  the  extensors.  The 
fibres  spread  out  as  they  descend,  and  are  interwoven  with  the 
annular  ligament  surrounding  the  head  of  the  radius. 

The  preceding  ligaments,  collectively,  form  a  continuous  cap- 
sule for  the  joint. 

It  must  be  remembered  that  the  strength  of  the  joint  depends 
upon  its  bony  formation. 

Superior  Radio-ulnar  Articulation.  —  The  orbicular  or  ati- 
nular  ligament  of  the  radius  forms  about  three-fourths  of  a  ring. 
Its  ends  are  attached  to  the  anterior  and  posterior  borders  of 
the  lesser  sigmoid  cavity  of  the  ulna,  and  is  broader  in  the 
middle  than  at  either  end.  Its  lower  border  is  straight ;  its 
upper  border  is  convex,  and  connected  with  the  anterior  and  ex- 
ternal lateral  ligaments.  With  this  sigmoid  cavity  it  forms  a 
complete  collar,  which  encircles  the  head,  and  part  of  the  neck, 
of  the  radius.  The  lower  part  of  the  ring  is  narrower  than  the 
upper,  the  better  to  clasp  the  neck  of  the  radius,  and  maintain 
it  more  accurately  in  position. 

Synovial  membrane  of  the  elboiv-joint.  Open  the  joint  by  a 
transverse  incision  in  front,  and  observe  the  relative  adaptation 
of  the  cartilaginous  surfaces  of  the  bones.  The  synovial  mem- 
brane lines  the  interior  of  the  capsule,  and  forms  a  cul-de-sac 
between  the  head  of  the  radius  and  its  annular  ligament.  It  is 
widest  and  loosest  under  the  tendon  of  the  triceps.     Where  the 


INFERIOR    RADIO-ULNAR    ARTICULATION.  4O9 

membrane  is  reflected  from  the  bones  upon  the  ligaments,  there 
is  more  or  less  adipose  tissue,  particularly  in  the  fossae  on  the 
front  and  back  part  of  the  lower  end  of  the  humerus. 

The  only  movements  permitted  between  the  humerus  and  the 
ulna  are  those  of  flexion  and  extension,  both  of  which  are  limited 
by  the  ligaments  and  tendons  in  front  of  and  behind  the  joint, 
and  probably  not  by  the  coronoid  and  olecranon  processes. 
The  head  of  the  radius  is  most  in  contact  with  the  capitellum 
of  the  humerus  during  semiflexion  and  semipronation  ;  and  it  is 
kept,  by  the  strong  orbicular  ligament  which  surrounds  the  neck 
of  the  radius,  from  being  dislocated  forwards  by  the  biceps.  The 
movement  at  the  superior  radio-ulnar  articulation  is  that  of  rota- 
tion in  the  lesser  sigmoid  cavity  of  the  ulna,  forming  an  example 
of  a  lateral  ginglymus  or  diarthrosis  rotatoria.  It  is  by  this  ro- 
tation of  the  head  of  the  radius  that  the  hand  is  carried  through 
an  extensive  range  of  pronation  and  supination  ;  for  it  is  articu- 
lated only  to  the  lower  end  of  the  radius,  the  ulna  being  excluded 
by  the  interarticular  fibro-cartilage  from  taking  any  share  in  the 
movement  at  the  wrist-joint. 

Interosseous  Membrane  or  Mid  Radio-ulnar  Union.  — 
This  is  an  aponeurotic  septum,  stretched  between  the  interosse- 
ous ridges  of  the  radius  and  ulna,  of  which  the  chief  purpose  is 
to  afford  an  increase  of  surface  for  the  attachment  of  muscles. 
The  septum  is  deficient  above,  beginning  about  an  inch  {2.^  cm.) 
below  the  tubercle  of  the  radius,  and  thus  permits  free  rotation 
of  that  bone.  Its  fibres  extend  obliquely  downwards  from  the 
radius  to  the  ulna.  It  is  perforated  in  its  lower  third  by  the 
anterior  interosseous  vessels. 

The  name  of  round  or  oblique  liganioit  is  given  to  a  thin  band 
(  f  fibres,  which  extends  obliquely  between  the  bones  of  the  fore- 
arm in  a  direction  contrary  to  those  of  the  interosseous  membrane. 
It  is  attached,  superiorly,  to  the  front  surface  of  the  ulna,  near 
the  outer  side  of  the  coronoid  process ;  inferiorly,  to  the  radius 
immediately  below  the  tubercle.  Between  this  ligament  and 
the  upper  border  of  the  interosseous  membrane  is  a  triangular 
interval  through  which  the  posterior  interosseous  artery  passes 
to  the  back  of  the  forearm.  A  bursa  intervenes  between  the 
oblique  ligament  and  the  insertion  of  the  tendon  of  the  biceps. 
The  use  of  this  ligament  is  to  limit  supination  of  the  radius. 

Inferior  Radio-ulnar  Articulation. — This  joint  is  a  lateral 
ginglymus,  and  is  formed  by  the  inner  concave  surface  of  the 
lower  end  of  the  radius  rotating  upon  the  convex  head  of  the 


4IO 


INFERIOR    RADIO-ULNAR    ARTICULATION. 


ulna  ;  which  mechanism  is  essential  to  the  pronation  and  supina- 
tion of  the  hand.  These  corresponding  surfaces  are  encrusted 
with  a  thin  layer  of  cartilage,  and  are  provided  with  a  very  loose 
synovial  membrane.  The  surfaces  are  maintained  in  position 
by  an  anterior  and  a  posterior  radio-ulnar  ligament,  and  a  triangu- 
lar fibro-cartilage. 

The  anterior  radio-iilnar  ligament  is  a  thin  fasciculus  extend- 
ing obliquely  inwards  from  the  anterior  border  of  the  sigmoid 
cavity  of  the  radius  to  the  head  of  the  ulna. 

^\\Q  posterior  radio-ulnar  lig- 
ament passes  from  the  poste- 
rior border  of  the  sigmoid  cav- 
ity to  the  posterior  surface  of 
the  styloid  process  of  the  ulna. 
'Y\\Q.tria7igtilar fibro-cartilage 
between  the  radius  and  ulna  is 
the  principal  uniting  medium 
between  the  bones.  To  see  it, 
saw  through  the  bones  of  the 
forearm,  and  separate  them  by 
cutting  through  the  interosse- 
ous membrane,  and  opening  the 
synovial  membrane  of  the  joint 
between  the  lower  ends.  Thus 
a  good  view  is  obtained  of  the 
fibro-cartilage  which  connects 
them  (Fig.  153).  It  is  triangu- 
lar, and  placed  transversely  at 
the  lower  end  of  the  ulna,  fill- 
ing up  the  interval  caused  by 
the  greater  length  of  the  radius. 
Its  base  is  attached  to  the  lower 
end  of  the  radius  ;  its  apex  to  a 
depression  at  the  root  of  the  styloid  process  of  the  ulna.  It  is 
thin  at  the  base  and  centre,  thicker  at  the  apex  and  sides.  Its 
upper  surface  is  in  contact  with  the  ulna,  and  covered  by  the 
synovial  membrane  of  the  inferior  radio-ulnar  joint  ;  its  lower 
surface,  forming  a  part  of  the  wrist-joint,  is  contiguous  with  the 
cuneiform  bone.  Its  borders  arc  connected  with  the  anterior 
and  posterior  ligaments  of  the  wrist.  In  some  instances  there 
is  an  aperture  in  the  centre.  When,  from  accident  or  disease, 
this  fibro-cartilage  gets  detached   from   the  radius,  the  conse- 


FiG.  153.  —  Diagram  of  the  Ligaments 
AND  Synovial  Membhanes  of  the  Wrist- 
joint. 

1.  External  lateral  ligament.  2.  Internal  lat- 
eral ligament.  3.  Interarticular  fibro-carti- 
lage between  radius  an;l  ulna.  4.  Interosseous 
ligaments.  5.  Lateral  ligaments  of  the  inter- 
carpal joint. 


RADIO-CARPAL    OR    WRIST-JOINT.  4II 

quence  is  an  abnormal  projection  of  the  lower  end  of  the 
ulna. 

The  synovial  membrane  of  this  joint  is  distinct  from  that  of 
the  wrist,  except  in  the  case  of  a  perforation  through  the  fibro- 
cartilage.  On  account  of  its  great  looseness,  necessary  f(jr  the 
free  rotation  of  the  radius,  it  is  called  mcmbratia  sacciformis. 

The  movement  between  the  lower  ends  of  the  radius  and  ulna 
is  due  to  the  rotation  of  the  radius  round  the  articular  head  of 
the  ulna,  and  is  confined  to  rotation  forwards  ox  pronation,  and 
to  rotation  backwards  or  supination  ;  the  extent  of  movement 
being  limited  by  the  anterior  and  posterior  ligaments. 

The  area  described  by  this  joint  in  pronation  and  supination 
is  one  hundred  and  thirty-five  degrees  ;  it  must  not  be  forgotten, 
however,  that  this  is  increased  by  the  rotation  at  the  shoulder 
joint.  ^  A.  H. 

Radio-carpal  or  Wrist-joint.  — This  is  an  arthrodial  joint  of 
condyloid  variety,  and  is  formed  :  above,  by  the  lower  end  of  the 
radius  and  the  distal  surface  of  the  triangular  fibro-cartilage  as 
the  receiving  cavity ;  below,  by  the  scaphoid,  semilunar  and 
cuneiform  bones  as  the  condyle,  the  two  former  articulate  with 
the  two  facets  on  the  radius,  the  latter  with  the  fibro-cartilage. 
The  joint  is  secured  by  an  anterior,  a  posterior  and  two  lateral 
ligaments. 

The  external  lateral  ligametit  extends  from  the  tip  of  the  styloid 
process  of  the  radius  to  the  outer  side  of  the  scaphoid  bone,  to 
the  anterior  annular  ligament,  and  to  the  trapezium. 

The  internal  lateral  ligament  is  round,  and  proceeds  from  the 
extremity  of  the  styloid  process  of  the  ulna  to  the  cuneiform 
bone.  Another  fasciculus  is  attached  to  the  pisiform  bone  and 
the  anterior  annular  ligament. 

The  anterior  ligament  consists  of  two  or  more  broad  bands  of 
ligamentous  fibres,  which  extend  from  the  lower  end  of  the  radius 
to  the  first  row  of  carpal  bones,  except  the  pisiform. 

The  posterior  ligamejit,  weaker  than  the  preceding,  proceeds 
from  the  posterior  surface  of  the  lower  end  of  the  radius,  and  is 
attached  to  the  posterior  surfaces  of  the  first  row  of  carpal 
bones. 

The  synovial  membrane  lines  the  under  surface  of  the  triangu- 
lar fibro-cartilage  at  the  end  of  the  ulna,  is  reflected  over  the 
several  ligaments  of  the  joint,  and  thence  upon  the  first  row  of 
the  carpal  bones  (Fig.  153). 

This  articulation  allows  of  all  the  movements  of  enarthrodial 


412  CARPAL    JOINTS. 

joints,  except  that  of  rotation  :  tluis,  it  allows  of  flexion,  exten- 
sion, abduction,  adduction,  and  circumduction,  so  that  it  is, 
strictly  speaking,  only  an  arthrodial  joint. 

Carpal  Joints.  —  The  bones  of  the  carpus  are  arranged  in 
two  rows,  an  upper  and  a  lower,  adapted  to  each  other  so  as  to 
form  between  them  a  joint.  The  articulations  may  be  best 
arranged  in  three  sets :  those  between  the  carpal  bones  of  the 
first  row  ;  between  those  of  the  second  row  ;  and  the  articula- 
tion of  the  two  rows  with  each  other  :  they  are  all  examples  of 
arthrodial  joints. 

a.  The  Jzrst  row  of  carpal  bojtes  are  connected  together  by 
two  palmar,  two  dorsal,  and  two  interosseous  ligaments. 

The  dorsal  diVid  palmar  transverse  ligaments  proceed,  on  the 
dorsal  and  palmar  aspects,  from  the  scaphoid  to  the  semilunar 
bone,  and  from  the  semilunar  to  the  cuneiform  bone  :  the  dorsal 
being  the  stronger  ;  the  ijitcrosseons  ligaments  connect  the  semi- 
lunar with  the  bones  on  each  side  of  it  (Fig.  153). 

The  pisiform  bone  is  articulated  to  the  palmar  surface  of  the 
cuneiform  bone,  to  which  it  is  united  by  a  fibrous  capsule. 
Inferiorly,  it  is  attached  by  two  strong  ligaments,  the  one  to 
the  unciform  bone,  the  other  to  the  carpal  end  of  the  fifth 
metacarpal  bone.  This  articulation  has  a  distinct  synovial 
membrane. 

b.  The  second  row  of  carpal  bones  is  connected  by  three 
dorsal,    three    palmar,    and    two  interosseous    ligaments. 

The  dorsal  and  palmar  ligaments  pass  transversely  from  one 
to  the  other.  There  are  usually  two  interosseous  ligaments,  one 
on  either  side  of  the  os  magnum  ;  sometimes  there  is  a  third, 
between  the  trapezium  and  trapezoid  bones  ;  they  are  thicker 
and  stronger  than  those  of  the  upper  row,  and  unite  the  bones 
more  firmly  together. 

c.  The  first  row  of  carpal  bones  is  arranged  in  the  form  of 
an  arch,  as  a  receiving  cavity,  so  as  to  receive  the  correspond- 
ing surfaces  of  the  os  magnum  and  unciforme,  as  a  condyle. 
External  to  the  os  magnum,  the  trapezium  and  trapezoid  bones 
present  a  slightly  concave  surface,  which  articulates  with  the 
scaphoid.  In  this  way  a  joint,  admitting  of  flexion  and  exten- 
sion only,  is  formed  between  the  upper  and  lower  row. 

The  tzvo  rows  of  carpal  bones  arc  connected  together  by 
palmar  and  dorsal  ligaments,  and  by  an  external  and  an  internal 
lateral  ligament. 

The  palmar  ligaments  consist  of  strong  ligamentous  fibres, 


CAKl'O-MKTACAKPAL    JOINTS.  4I3 

which  pass  obliquely  from  the  bones  of  the  first  to  those  of  the 
second  row. 

The  dorsal  ligaments  consist  of  oblique  and  transverse  fibres 
which  connect  the  dorsal  surfaces  of  the  bones  of  the  upper 
with  the  lower  row. 

The  external  lateral  ligament,  very  distinct,  passes  from  the 
scaphoid  to  the  trapezium  :  the  internal  lateral  ligament  from 
the  cuneiform  to  the  unciform. 

Divide  the  ligaments  to  see  the  manner  in  which  the  carpal 
bones  articulate  with  one  another.  Their  surfaces  are  crusted 
with  cartilage,  and  have  a  comjnon  synovial  membrane  which  is 
very  extensive  and  lines  the  distal  surfaces  of  the  scaphoid, 
semilunar,  and  cuneiform  bones ;  it  then  passes  forwards  be- 
tween the  trapezium  and  trapezoid,  the  trapezoid  and  os  mag- 
num, the  OS  magnum  and  the  cuneiform  to  the  articulations  be- 
tween the  second  row  of  carpal  bones  and  the  metacarpal  bones 
of  the  four  fingers  (Fig.  153). 

Joints  between  Trapezium  and  the  First  Metacarpal 
Bone.  —  The  trapezium  presents  a  cartilaginous  surface, 
convex  in  the  transverse,  and  concave  in  the  antero-pos- 
terior  direction  {i.e.,  saddle-shaped),  which  articulates  with  the 
cartilaginous  surface  on  the  metacarpal  bone  of  the  thumb,  con- 
cave and  convex  in  the  opposite  directions.  This  peculiar 
adaptation  of  the  two  surfaces  permits  the  several  movements 
of  the  thumb — viz.,  flexion,  extension,  abduction,  and  adduc- 
tion ;  consequently  circumduction.  It  is  an  arthrodial  joint, 
but  permits  of  such  extensive  movement,  that  it  is  described  by 
some  anatomists  as  one  by  "reciprocal  reception."  Thus  we 
are  enabled  to  oppose  the  thumb  to  all  the  fingers,  which  "is  one 
of  the  great  characteristics  of  the  human  hand.  The  joint  is 
surrounded  by  a  eapsnlar  ligament  sufficiently  loose  to  admit 
free  motion,  and  stronger  on  the  dorsal  than  on  the  palmar 
aspect.  The  security  of  the  joint  is  increased  by  the  muscles 
which  surround  it.      It  has  a  separate  syjiovial  membrane. 

Carpo-metacarpal  Joints. — The  metacarpal  bones  of  the 
fingers  are  connected  to  the  second  row  of  the  carpal  bones  by 
ligaments  upon  Xhoir  palmar  and  dorsal  surfaces,  and  by  inter- 
osseous ligaments. 

The  dorsal  ligaments  are  the  stronger.  The  metacarpal 
bone  of  the  forefinger  has  two  :  one  from  the  trapezium,  the 
other  from  the  trapezoid  bone.  That  of  the  middle  finger  has 
also  two,   proceeding  from   the  os  magnum  and  the  os  trape- 


414  SYNOVIAL    MEMBRANES    OF    THE    WRIST. 

zoides.  That  of  the  ring  finger  has  also  two,  proceeding  from 
the  OS  magnum  and  the  unciform  bone.  That  of  the  Httle 
finger  has  one  only,  from  the  unciform  bone. 

The  palmar  ligaments  are  arranged  nearly  upon  a  similar 
plan.  The  metacarpal  bone  of  the  forefinger  has  one  from  the 
trapezoid  bone.  That  of  the  middle  finger  has  three,  proceed- 
ing from  the  trapezium,  the  os  magnum,  and  the  unciform  bone. 
Those  of  the  ring  and  little  fingers  have  each  one,  from  the 
unciform  bone. 

Besides  the  preceding  ligaments,  there  are  some  of  consider- 
able strength,  called  the  interosseous.  They  proceed  from  the 
adjacent  sides  of  the  os  magnum  and  the  os  unciforme,  descend 
vertically,  and  are  fixed  into  the  radial  side  of  the  metacarpal 
bone  of  the  middle  and  ring  fingers  (Fig.  153).  This  ligament 
occasionally  isolates  the  synovial  membrane  of  the  two  inner 
metacarpal  bones  from  the  common  synovial  membrane  of  the 
carpus. 

Separate  the  metacarpal  bones  from  the  carpus,  and  observe 
the  relative  form  of  their  contiguous  surfaces.  The  metacarpal 
bones  of  the  fore  and  middle  fingers  are  adapted  to  the  carpus 
in  such  an  angular  manner  as  to  be  almost  immovable.  The 
metacarpal  bone  of  the  ring  finger,  having  a  plane  articular 
surface  with  the  unciform  bone,  admits  of  more  motion.  Still 
greater  motion  is  permitted  between  the  unciform  and  the  met- 
acarpal bone  of  the  little  finger,  the  articular  surface  of  each 
being  slightly  concave  and  convex  in  opposite  directions.  The 
greater  freedom  of  motion  of  the  metacarpal  bone  of  the  little 
finger  is  essential  to  the  expansion  and  contraction  of  the 
palm. 

The  carpal  extremities  of  the  metacarpal  bones  of  the  fingers 
are  connected  with  each  other  by/^^/wrtrand  dorsal  transverse 
ligaments.  They  are  also  connected  by  interosseoics  ligaments, 
which  extend  between  the  bones,  immediately  below  their  con- 
tiguous cartilaginous  surfaces. 

The  distal  extremities  of  these  bones  are  loosely  connected  on 
their  palmar  aspect  by  the  transverse  metacarpal  ligament. 

Synovial  Membranes  of  the  Wrist. — There  are  five, 
sometimes  six,  distinct  synovial  membranes,  proper  to  the 
lower  end  of  the  radius,  and  the  several  bones  of  the  carpus 
(Fig.  153,  p.  410),  as  follows:  — 

a.  One  between  the  lower  end  of  the  radius  and  the 
ulna. 


FIRST    JOINT    OF    THE    FINGERS.  4I 5 

b.  One    between    the    radius    and    the    first    row    of   carpal 

bones. 

c.  One  between  the  trapezium  and  the  metacarpal  bone  of 

the  thumb. 

d.  One  between  the  cuneiform  and  pisiform  bones. 

e.  One  between  the  first  and  second  rows  of  carpal  bones 

(the  intercarpal  joint).  This  extends  to  the  metacarpal 
bones  of  the  four  inner  fingers. 

The  interosseous  ligament  between  the  os  magnum  and  ring 
finger  occasionally  shuts  off  the  synovial  membrane  between 
the  unciform  and  two  inner  metacarpal  bones  from  the  large 
intercarpal  sac  ;  thus  making  the  sixth  distinct  synovial  mem- 
brane. 

First  Joint  of  the  Fingers.  —  The  first  phalanx  of  the 
finger  presents  a  shallow  oval  receiving  cavity,  crusted  with 
cartilage,  with  the  broad  diameter  in  the  transverse  direction,  to 
articulate  with  the  round  condyloid  cartilaginous  head  of  the 
metacarpal  bone,  of  which  the  articular  surface  is  elongated  in 
the  antero-posterior  direction,  and  of  greater  extent  on  its 
palmar  than  its  dorsal  aspect.  This  formation  of  parts  permits 
flexion  of  the  finger  to  a  greater  degree  than  extension  ;  and 
also  a  slight  lateral  movement. 

Each  joint  is  provided  with  two  strong  lateral  ligaments,  and 
an  anterior  or  pahnar  ligament. 

The  lateral  ligaments  arise  from  the  tubercles  on  either  side 
of  each  metacarpal  bone,  and,  inclining  slightly  forward,  are 
inserted  into  the  sides  of  the  base  of  the  first  phalanx  of  the 
finger. 

The  anterior  (glenoid)  ligament  is  a  thick,  compact,  fibrous 
structure,  which  extends  over  the  palmar  surface  of  the  joint 
between  the  lateral  ligaments.  Its  distal  end  is  firmly  attached 
to  the  base  of  the  first  phalanx  of  the  finger ;  its  proximal  end 
is  loosely  adherent  to  the  rough  surface  above  the  head  of  the 
metacarpal  bone.  On  either  side  it  is  inseparably  connected 
with  the  lateral  ligaments,  so  that  with  them  it  forms  a  strong 
capsule  over  the  front  and  sides  of  the  joint.  Its  superficial 
surface,  firmly  connected  with  the  transverse  ligament,  is 
slightly  grooved  for  the  play  of  the  flexor  tendons  ;  its  deep 
surface  is  adapted  to  cover  the  head  of  the  metacarpal  bone. 
Two  sesamoid  bones  are  found  in  the  palmar  ligament  belong- 
ing to  the  joint  between  the  metacarpal  bone  and  the  first 
phalanx  of  the  thumb. 


4l6  SECOND    AND    LAST    JOINT    OF    THE    FINGERS, 

The  palmar  ligaments  have  a  surgical  importance  for  the 
following  reason  :  In  dislocation  of  the  fingers,  the  facility  of 
reduction  mainly  depends  upon  the  extent  to  which  the  glenoid 
ligament  is  injured.  If  it  be  much  torn,  there  is  but  little 
difficulty  :  if  entire,  the  reduction  may  require  much  manip- 
ulation. 

These  joints  are  secured  on  their  dorsal  aspect  by  the  ex- 
tensor tendon,  and  the  expansion  proceeding  from  it  on  either 
side.  Their  synovial  membranes  are  loose,  especially  beneath 
the  extensor  tendons. 

Second  and  Last  Joint  of  the  Fingers.  —  The  correspond- 
ing articular  surfaces  of  the  phalanges  of  the  fingers  and  thumb 
are  so  shaped  as  to  form  a  hinge-joint  {ginglymus),  and,  there- 
fore, incapable  of  lateral  movement.  The  ligaments  connecting 
them  are  similar  in  every  respect  to  those  between  the  meta- 
carpal bones  and  the  first  phalanges.  The  palmar  ligament  of 
the  last  joint  of  the  thumb  generally  contains  a  sesamoid 
bone. 

The  wrist-joint  is  a  complex  articulation,  in  which  the  seat  of 
movement  is  partly  in  the  radio-carpal,  and  partly  in  the  inter- 
carpal articulation.  Thus  the  hand  at  the  radio-carpal  joint  is 
capable  of  extension  (dorsi-flexion)  and  flexion,  the  latter  being 
the  most  free ;  it  is  also  capable  of  adduction  (ulnar  flexion)  and 
of  abduction  (radial  flexion)  to  a  lesser  extent.  Between  the 
carpal  bones  and  carpo-metacarpal  bones,  the  movement  which 
takes  place  when  the  hand  is  pressed  down  so  as  to  support  the 
weight  of  the  body,  is  that  of  separation  of  the  anterior  part  of 
their  apposed  surfaces  ;  undue  separation  being  prevented  by 
the  interosseous  and  palmar  ligaments.  The  articulation  be- 
tween the  unciform  and  fourth  and  fifth  metacarpals  is  not  so 
firm  as  that  between  the  other  carpo-metacarpal  bones,  conse- 
quently there  is  greater  freedom  of  motion  forwards,  seen  in 
deepening  the  palm  and  in  shutting  the  hand.  The  movements 
at  the  metacarpo-phalangeal  articulation  are  those  of  extension 
and  flexion,  of  adduction  and  abduction,  the  two  latter  being 
most  marked  in  extension  of  the  finger.  Between  the  thumb 
and  trapezium  all  the  movements  of  an  enarthrodial  joint 
exist,  except  that  of  rotation  ;  a  little  rotation  probably  takes 
place  when  the  metacarpal  bone  is  flexed.  In  the  inter- 
phalangeal  and  phalangeal  joints,  the  only  movements  per- 
mitted are  those  of  extension  and  flexion. 


INDEX 


Abdomen,  topography   of    viscera   of, 

184,  185,  186.  187 
Abducens,  nerve,  36,  75, 
Adami,  pomum,  253 
Adventitia  oculi,  64 
Alveolar  point,  24 
Amygdala  tonsili,  248 
Angular  artery,  56 

vein,  56 
Annular  ligament  of  hand.  360 

posterior    ligament     of     forearm, 

387 
Annulus  ovalis,  214 
Ansa  hypoglossi,  loi,  124 
Ant  run,  Highnore,  281 
Aorta,  abdominal,  192 
arch,  course  of,  192 

descending  thoracic,  194.  198, 
great  sinus  of,  194 
relations  of,  192 

to  sternum,  195 
ascending  part  of,  192 
descending  part  of,  194 
transverse  part  of,  194 
Aponeurosis,  epicranial,  20 
lumbar,  373 
pharyngeal,  239,  242 
supra-hyoid,  108 
vertebral,  284,  373 
Apparatus  ligamentosus  colli,  300 
Aquxductus  Fallopii,  60,  275 
Arachnoid,  cavity  of,  26 
Arantius,  corpus  of,  218 

nodules  of,  218 
Arch,  palmar,  357 

Arm,  upper,  cutaneous  nerves  of,  308, 
326 

musculo-cutaneous    nerve  of,    336, 

341 

surface  marking  of,  307,  326 
Arnold's  ganglion,  159.  271 

ner\e,  24,  160 
Arteries :  — 

acromial  thoracic,  311,  319 

alar  thoracic,  316,  319 

alveolar,  149 


Arteries :  — 

anastomotica    magna   of   brachial, 

335'  3«6 
angular,  56 
anterior  cerebral,  277 
aorta,  192 

abdominal,  192 
arch  of,  192 

ascending,  192 
descending,  194 
transverse,  194 
relations  of,    to  sternum, 

195 
descending  thoracic,  198 

arteriae  receptaculi,  277 
articular,  of  shoulder,  135 
attachment  to  ventricles,  224 
auricular  anterior,  141 

posterior,  22,  122,  142 
axillary,  312,  317 
back, 294 
bicipital,  320 
brachial,  332 
brachio  cephalic,  195 
bronchial,  209,  236 
buccal,  149 
carotid,  common,  96,  98 

difference    between    left    and 
right,  98 

external,  58,  109,  112 

internal,  39,  157,  277 

left  common,  196 
carpal  of  radial,  anterior,  349 

posterior,  349,  397 

ulnar,  anterior,  351 

posterior,  351,  397 
centralis  retinae,  72 
cerebral  anterior,  277 

middle,  277 
cervical  ascending,  135 

deep,  294 

superficial,  135 

transverse,  135 
cervicis  princeps,  122,  294 

profunda,  136 
choroid  anterior,  277 
ciliary  anterior,  72 

long,  72 


417 


4i8 


INDEX. 


Arteries :  — 

ciliary  short,  72 
circulus  major,  72 

minor,  72 
circumflex  of  arm,  anterior,  320 

posterior,  319,  380 
clavicular,  312 
conies  nervi,  mediani,  355 

phrenici,  172 
coronary,  194,  222 

of  lip,  inferior,  56 

superior,  56 
cranial,  122 
crico  thyroid,  1 11 
deep  cervical,  137,  294 

palmar  arch,  367 

temporal,  149 
dental  anterior,  150 

inferior,  149 

superior,  150 
digital,  of  hand.  359 
dorsalis  indicis,  397 

lingua;,  1 21 

pollicis,  397 

scapulae,  319,  383 
dorsal  interosseous  of  hand,  397 
dural,  124 

mididural,  33,  148 

postdural,  23^  122 

parvidural,  149 

predural,  33 
ethmoidal  anterior,  73 

posterior,  73 
external  mammaiy,  319 
external  maxillary,  54 
facial,  54,  113 

anastomosis  of,  56 
frontal,  21,  64,  73 
glandular,  1 14 
hyoid,  1 1 1 

superior,  121 
hypogastric,  227 
inferior  coronary,  56 
inferior  dental,  149 
inferior  laljial,  55 
inferior  palatine,  114 
infraorbital,  62,  150 
infraspinous,  135,  375 
innominate,  195 
intercostal,  206 

anterior,  206 

collateral,  206 

dorsal  of,  207 

superior,  136 
interosseous,  anterior,  355 

common,  of  forearm,  351,  355 

of  hand, 355 


Arteries :  — 

posterior,  396 

recurrent,  396 
intraspinal,  294 
labial  inferior,  56 

superior,  56 
lachrymal,  64,  72 
laryngeal,  superior,  in 
lateral,  of  nose,  56 

spinal,  134 
lingual,  112,  121,  269 
long  ciliary,  72 
mammary,  internal,  136,  171 

branches  of,  172 
mandibular,  149 
masseteric,  148 
mastoid,  122,  123 
maxillary,  external,  54 

internal,  147 
mediastinal,  176 

posterior,  209 
meningea  media,  148 

parva,  33,  149 
meningeal,  ;^3,  124 

anterior,  33,  277 

middle,  33,  148 

posterior,  ^3^  122 
mental,  63 

middle  temporal,  142 
mididural,  148 
muscular  to  eye,  73 
musculophrenic,  172 
mylohyoid,  149 
nasal,  73,  150,  283 
nutrient  of  humerus,  335 
occipital,  21,  22,  122,  294 
a-sophageal,  202,  209 
ophthalmic,  72,  277 
oibital,  149 
palatine,  ascending,  114,  156 

descending,  150 
palmar  arch,  deep,  367 

superficial,  357 

interosseous,  367 
palmaris  profunda,  366 
palpebral,  inferior,  73 

superior,  73 
perforating,  of  hand,  367 

intercostal,  172 
pericardiac,  172 
petrosal,  33,  149 
pharyngeal,  ascending,  123,  158 

meningeal  of,  124,  159 

pharyngeal    branches  of,  123, 

159 
posterior  auricular,  21,  22 
piofunda  inferior,  335 


INDEX. 


419 


Arteries:  — 

profunda  superior,  334,  386 
princeps  pollicis,  366 

cervicis,  122,  294 
pterygoid,  149 
pterygopalatine,  150 
pulmonary,  209,  236 
radial,  347 

in  palm,  366 

at  back  of  wrist,  397 

recurrent,  348 
radialis  indicis,  366 
ranine,  121 
receptaculi,  39,  277 
scalp,  of,  21 

scalpulK  dorsalis,  319,  383 
scapula,  posterior,  135,  376 

supra-,  135,  375,  384 
septum  of  the,  56,  150 
short  ciliary,  72 
spheno-palatine,  150 
spinal  lateral,  134 
sternal,  172 
sterno  mastoid,    inferior.    87.    135, 

375 

middle,  11 1 

superior,  122 
stylomastoid,  123 
subclavian,  left,  130,  196 

right,  127 

branches  of,  133 
sublingual,  121 
submental,  114 
subscapular,  135,  319,  375 
superficialis  volae,  349 

colli,  135,  370,  373,  376 
supra-acromial,  135 
supra-orbital,  21,  72 
supra-scapular,  135,  383 

subscapular  of,  135 
temporal,  21,  22,  141,  142 

deep,  ^2^  149 

superficial,  22,  i  42 
thoracica-acromialis,  310,  311.  319 

alaris,  316,  319 

longa,  319 

superior,  311,  319 
thymic,  172 
thyroid  axis,  135,  375 

inferior,  135,  265 

superior,  in,  265 
tonsillar,  1 14 
transverse  cervical,  135 

colli,  135 

facial,  57 

humeri,  375 
tympanic,  148 


Arteries:  — 

ulnar,  349 

anterior  recurrent,  351 
posterior  recurrent,  351 

ulnaris,  profunda,  359 

vertebral,  133,  294 

lateral,  spmal  of,  134 

Vidian,  150 
Articulations,  acromio-clavicular,  402 

alio  axoid,  301 

carpal,  412 

carpo  metacarpal,  413 

costo  sternal,  304 

vertebral,  301 

elbow,  407 

inter-phalangeal,  415.  416 

lower-jaw,  305 

mandible,  305 

metacarpal,  414 

metacarpophalangeal,  415 

occipito-atlantal,  299 

radio-carpal,  41 1 

radioulnar,  inferior,  409 
superior,  409 

scapuloclavicular,  402 

shoulder,  404 

sternoclavicular,  400 

tempero  mandibular,  306 

trapezium  and  thumb,  413 

wrist  ,411 
Aryteno-epiglottideus,  262 

inferior,  265 

superior,  265 
Aryteno-epiglottidean  folds,  257,  258 
Arytenoid  cartilages,  255 
Arytenoideus,  263 
Asterion,  24 

Atrium  of  auricle,  214,  220 
Auditory  nerve,  36 
Aurem  attollens,  21 

attrahans,  21 

retrahens,  21 
Auricle  of  heart,  right,  214 

left,  220 

muscular  fibres  of,  224 
Auricular  appendix,  214,  220 

artery,  anterior,  141 
posterior,  22,  122 

great,  nerve,  82 
Auricular  nerve,  60,  160 

posterior,  24,  123 

auriculo-ventricular  opening,  214. 
216,  220,  221 

nerve  of  pneumogastric,  24 

vein,  22,  123 
Auriculotemporal  nerve,  23,58, 142,153 
Axilla,  dissection  of,  313 


42  o 


INDEX. 


Axilla,  boundaries  of,  314 

relations  in,  311 
Axillarj'  artery,  312,  317 

ligature  of,  312 

fascia,  313 

plexus  of  nerves,  321 

vein,  320 
Axis  thyroid,  135 
Azygos  veins,  199-200 


B. 


Back,  arteries  of,  294 

cutaneous  nerves  of,  367 

muscles,  of,  284,  367 

nerves  of,  292,  369 

veins,  294 
Band,  ventricular,  259 

vocal,  259 
Bartholin,  duct  of,  119 
Basilic  vein,  328 
Basion,  25 

Bell,  nerve  of,  325,  377 
Biceps  of  arm,  330,  405 
Bochdalek,  ganglion  of,  270 
Brachial  artery,  332 

plexus  of  nerves,  137,32 
Brachials  anticus,  332 
Brachio  cephalic  artery,  195 

veins,  190 
Brain,  membranes  of,  26 

removal  of,  30 
Bregma,  25 
Bronchi,  229 
Bronchial  arteries,  209,  236 

lymphatic  glands,  210 

veins,  237 
Bronchocele,  103 
Buccal  fascia,  54 

glands,  54 
Buccinator,  52 
Bucco  pharyngeal  fascia,  54 
Bursre,  biceps,  near  tendon  of,  406 

of  carpus,  365,  398 

over  knuckles,  386 
olecranon,  386 

under     coraco-acromial     ligament, 

379 
coraco-brachialis,  332 
deltoid,  379 
under  latissimus  dorsi,  372 
subacromial,  379 
subscapularis,  383 
subcutaneous,  386 
teres  maijor,  382 
triceps,  385 


Canal  of  Huguier,  154 
Canaliculus,  40,  49 
Canthi,  46 

Capsule  of  Tenon,  64,  76, 
Cardiac  nerves,  of  pneumogastric,  162, 
203 
sympathetic,  164,  204 
plexus,  deep,  204,  210,  211 
superficial,  204,  211 
Carotid  artery,  common,  96,  98,  198 
ligature  of,  98 
difference  of  left,  98 
external,  109 

branches  of,  no 
ganglion,  165 
internal,  39,  158,  277 

curves  of,  39 
plexii.s,  39,  165 
triangles,  91 
Carpal  arteries,  397 
Carpus,  bursal  sac  of,  365 
Cartilages,  arytenoid,  255 
cornicula  laryngis,  256 
cricoid,  254 
cuneiform,  256 
epiglottis,  256 
of  larynx,  253 
of  nose,  278 
sesamoideae,  278 
of  trachea,  229 
of  Wrisberg,  256 
tarsal,  48 
thyroid,  253 
Cartilago  triticea,  253 
Caruncula  lachrymalis,  46 
Cava,  vena,  inferior,  214 

superior,  191 
Cavernous  plexus,  40,  165 
sinus,  32,  37 

structures  passing  through,  38 
Cephalic  index,  25 
vein,  312,  328 
Cerebri,  falx,  28 
Cervicalis  ascendens  artery,  135 
profunda,  136 
superficialis,  135 
Cervical  fascia,  83 
deep,  84 

ganglion,  middle,  165 
inferior,  167 
Cervical  glands,  103 

plexus  of  nerves,  124 
deep,  124  • 
superficial,  82 
Cervicis  princeps  artery,  122 


INDEX. 


421 


Cervicofacial  nerve,  61 
Check  ligaments,  300 

of  eye,  65 
Chest,  of  female,  168 

surface  marking  of,  397 

diameters  of,  16S 
Chorda  tympani  nerve,  154,  276 
Chordce  tendineae  of  ventricles,  216 

vocales,  258 

Willisii,  30 
Chyli  receptaculum,  200 
Cilia,  46 

Ciliai7  arteries,  anterior,  72 
long,  72 
short,  72 

nerves,  long,  71 
Circular  sinus,  32,  37 
Circulation,  foetal,  225 
Circumflex  artery,  anterior,  320 
posterior,  320,  380 

nerve,  322,  381 
Clavicle,  307 

Collateral  circulation   after   ligature  of 
axillary  artery,  320 

carotid,  98 

innominate,  196 

subclavian,  133 
Columnas,  carneae,  216,  221 
Complexus,  289 

Communicantes  noni  nerves,  100,  124 
Conarium,  277 
Conjunctiva,  46 
Constrictors  of  pharynx,  239 
Conus  arteriosus,  216 
Cords,  vocal,  258 
Cornicula  laryngis,  256 
Coronary  arteries  of  heart,  222 

inferior,  56 

superior,  56 

plexuses,  204,  210,  211 
Coronary  sinus,  214,  222 
Corpus,  Arantii,  218 

triticeum,  253 
Costo-coracoid  membrane,  310 
Cotunnius,  nerve  of,  259 
Cranial  nerves,  dissection  to  expose,  34 

exit  of,  34 
Cricoid  cartilage,  254 

ligaments  of,  254 
Crista,  galli,  28 
Cuneiform  cartilages,  256 
Cuvier,  duct  of,  188 

D. 

Deglutition,  mechanism  of,  251 
Deltoid  muscle,  378 


Deltoid,  parts  covered  by,  379 
Dental  artery,  inferior,  149 
superior,  150 

nerve,  inferior,  1 53 
Diaphragm,  opening  in,  169 
Diaphragma  sella;,  30 
Digastric  muscle,  107 

triangle  and  contents,  108 
Diogenes,  cup  of,  356 
Dissection  of  the  :  — 

arm,  326 

axilla,  313 

back,  284 

muscles    of,    connected    with 
arm,  367 

brain,  to  remove,  30 

cavernous  sinus,  37 

cranial  cavity,  30 

cranial  nerves,  exit  of,  34 

digastric  triangle,  106 

epicranial  region,  26 

eye  muscles,  70 

extremity,  upper,  308 

face,  40 

forearm,  back,  386 
front,  341 

hand, 355 

heart,  212 

larynx,  252 

ligaments,  400 

maxillary  nerve,  superior,  369 

neck, 78 

nose,  278 

orbit,  63 

pharynx,  237 

pterygoid  region,  145 

shoulder  muscles,  377 

submandibular    or  digastric    trian- 
gle, 106 

supraclavicular  region,  89 

temporal  region,  140 

thorax,  169 

tongue,  266 
Dorsal  nerves,  207,  367 
Ducts,  or  duct,  of:  — 

Bartholin,  119 

Cuvier,  188 

nasal,  280 

parotid  gland,  59 

Rivinus,  1 19 

Steno's,  59 

sublingual  gland,  119 

thoracic,  200 

Wharton's,  154 
Ductus  arteriosus,  210,  227 

venosus,  227 
Dura,  26 


422 


INDEX. 


Dura,  layers  of,  26 
nerves  of,  26 
processes  of,  27 
sinuses  of,  29 
subduraJ  space,  26 


E. 

Ear,  muscles,  21 

Eighth  pair  of  nerves,  36 

Elbow-joint,  407 

synovial  membrane  of,  408 

triangle,  342 

veins  in  front  of,  328 
Eleventh  nerve,  37,  162 
Eminence,  hypothenar,  355 

thenar,  355 
Endocardium,  216,  219,  223 
Epicardium,  223 
Epicranial  aponeurosis,  20 
Epiglottis,  256 

cushion  of,  258 

ligaments  of,  261 

mucous  folds  of,  258 
Epipteric  bone  of  Flower,  25 
Eustachian  tube,  250 

valve,  215 
Eye,  check,  ligaments  of,  65 

lashes,  46 

lids,  45,  47 

muscles  of,  47 
Exit  of  the  cranial  nerves,  34 


F. 


Face,  dissection  of,  40 

motor  nerves  of,  40 

sensory  nerves  of,  40,  59,  62 
Facial  artery,  54,  113 

nerve,  36,  82,  275 
on  face,  59 

transverse  artery,  56 

vein,  56,  109 
Fallopii  acjueductus,  60,  275 
Falcula,  28 
Falx,  28 

Fascia,  arm,  308,  329 
forearm,  342 
back  of  foreaiTn,  387 

axillary,  313 

buccal,  54 

buccopharyngeal,  54 

cervical,  79,  80,  83 

costo-coracoid,  310 

intermuscular  of  arm,  308,  329 


Fascia,  lumbar,  285 

metacarpus,  3S8 

muscular  of  arm,  329 
of  neck,  84 

orbit,  64 

palmar,  356 

pharyngeal,  239 

prevertebral,  84 

semilunar  of  biceps,  328 

temporal,  143 
Faucium  isthmus,  243 
Fibro  cartilages,     interarticular,    lower 
jaw,  306 

intervertebral,  297 

scapulo-clavicular,  401 

sterno-clavicular,  400 

wrist,  410 
Fifth  cranial  nerve,  35,  150,  269 
Fissures,  palpebral,  46 

sphenoidal,  nerves  in,  38 
FcEtal  circulation,  226 

changes  at  birth,  227 
Folds,  ary-epiglottic,  258 

glosso-epiglottic,  267 
Foramen  ovale  of  heart,  214,  225 

quadratum,  169 

Thebesius,  216 
Forearm,  cutaneous  nerve  of,  341 
back  of,  387 

deep  fascia  of,  342 

fascia  on  back  of,  387 

surface  marking  of,  340 
Fornix,  conjunctivae,  46 
Fossa,  Mohrenheim's,  78 

nasal,  243 

ovalis,  214 
Fourth  cranial  nerve,  34,  64,  65,67 
Fra:num  linguae,  267 
Frontal  artery,  21,  64,  73 

nerve,  64,  66 


Ganglion  of  Andersch,  157,  274 
Arnold,  159,  271 
Bochdalek,  270 
cardiac,  211 
carotid,  165 
cervical  inferior,  167 

middle,  165 

superior,  164 
Ehrenritter,  157,  274 
Gasserian,  35,  269 
geniculate  of  facial,  39,  275 
impar,  164 
jugular,  157,  274 


INDEX. 


423 


Ganglion,  lenticular,  73 

Meckel's,  250,  271 

ophthalmic,  73 

otic,  272 

petrous,  157,  274 

pneumogastric,  root  of,  159.  160 
trunk,  159,  160,  275 

Ribes,  164 

sphenopalatine,  24S,  270,  271 

submaxillary  or  submandibular,  1 20 

Wrisberg,  21 1 
Gasserian  ganglion,  35,  269 
Glabella,  25 
Glands,  of  axilla,  313,  315 

buccal,  54 

glandula;  concatenatae,  103 

intercostal,  209 

lachrymal,  67 

lingual,  268 

mammary  artery,  with,  172 

Meibomian,  47,  49 

molar,  54 

oesophageal,  203 

parotid,  57 

sublingual,  119 

submaxillary  or  submandibular,  109 

thyroid,  10 1 

tracheal,  230 

lymphatic  axillary,  315 

bronchial,  210 

at  elbow,  329 

of  heart,  223 

intercostal,  209 

mediastinal,  anterior,  175 

neck,  deep,  103 
superticial,  8r 

submandibular,  114 
Glandula  socia  parotidis,  59 
Glandulae  concatenata;,  103 

Pacchioni,  28 

palatinae,  251 
Glosso-epiglottic  folds,  257,  258,  267 
Glossopharyngeal  nerve,  36,  156,  269 
Glottidis  rima,  259 
Glottis,  259 

muscles  acting  on,  265 
Gustatory  n.,  120 


H. 

Hand,  dissection  of  palm,  355 

surface  marking,  355 
Hasaer,  valve  of,  2S0 
Heart  auricle,  left,  220 
right,  214 
cavities,  thickness  of,  225 


Heart  chorda;  tendinea:,  216 

columnar  carnea;,  216,  221 

endocardium,  2  1  4 

fibrous  rings  of,  223 

infundibulum,  or  cornus  arteriosus, 
216 

lymphatics  of,  223 

muscular  fibres  of,  224 

musculi  papillares,  217,  221 

musculi  peclinati,  214,  216,  220 

nerves  of,  210,  223 

openings,  size  of,  222 

position  of,  169,  182,  188,  212 

size  of,  213 

valves  of,  169,  181,  189 

veins  of,  222 

ventricles,  left,  221 
right,  216 

weight  of,  213 
Herophili,  torcular,  29 
Highnore,  antra, -281 
Hilum  pulmonis,  178 
Hilton's  muscle,  262 
Huguier,  canal  of,  154 
Hypoglossi  ansa,  loi,  124 
Hypoglossal  nerve,  37,  109,  117,  163 
Hypophisis,  30 
Hypothena,  355 
Hyoides  os,  252 

basi-hyal,  252 

cerato-hyals,  252 

ligaments  of,  252 

thyro-hyals,  252 


I. 


Ilio  costalis,  288 
Inferior  cervical  ganglion,  167 
Infraclavicular  triangle,  310 
Infra-orbital  artery,  62,  150 

nerve,  62 
Infundibulum  of  heart,  216 

nose,  280 
Inion,  25 
Innominate  artery,  195 

veins,  190 
Interarticular  fibro  cartilages  {See  Fibro- 

cartilages) 
Intercostal  arteries,  206 
anterior,  206 
collateral,  206 
dorsal,  207 
superior,  136 
glands,  209 
muscles,  205 
nerves,  208 


424 


INDEX. 


Intercosto-humeral  nerves,  314 
Interpleural  space,  175 
Intervertebral  fibro-cartilages,  297 
Intumescentia  gangliformis,  275 
Isthmus  faucium,  243 


Jacobson,  nerve  of,  274 
Jaw,  lower,  ligaments  of,  155 
joints  {St-e  Articulations) 
Jugular  ganglion,  157,  274 
vein,  anterior,  81 

external,  58,  80 

internal,  99 

posterior  external,  81 


Labial  arteries,  56 

nerves,  62,  153 
Lachrymal  gland,  67 
nerve,  66,  67 
sac,  48,  280 
Lacus  lachrymalis,  46 
Lambda,  25 
Larynx,  252 

arteries,  262 
cartilages,  253,  257 
cavity,  258 

male  and  female,  266 
mucous  membrane  of,  257 
muscles,  262 
nerves,  ill,  265 
situation  of,  252 
upper  opening  of,  258 
ventricle  of,  261 
Laryngotomy,  105 
Lateral  sinuses,  31 
Latissimus  dorsi,  323,  370 
Lenticular  ganglion,  73 
Ligamenta  annularia,  360,  364 

vaginalia,  364 
Ligaments  of :  — 

accessory  of  shoulder.  405 
acromioclavicular,  inferior,  403 

superior,  402 
annular  carpus  anterior,  360 
radius,  408 

posterior  of  wrist,  387 
anterior  carpal,  41 1 
common,  296 
elbow,  407 
wrist,  411 
atlo-axoid,  anterior,  300 


Ligaments  of:  — 

atlo  axoid,  posterior,  300 

between    occipital    bone    and 
atlas,  299 
calcaneo-cuboid,  capsular,  299,  302 
carpo-metacarpal,  413 
dorsal,  413 
palmar,  414 
interosseous,  414 
carpus,  412 
check,  300 
common,  anterior  vertebral,  296 

posterior  vertebral,  296 
conoid,  403 
coracoacromial,  403 
clavicular,  403 
humeral,  405 
coracoid,  403 
costo-clavicular,  401 
sternal,  304 
transverse,  304 
vertebral,  303 
crico-arytenoid,  254 
crico-thyroid,  254 
of  neck,  300 
cruciata,  364 
cruciform,  300 
dissection  of,  400 
elbow,  anterior  and  posterior,  407 
lateral  external,  408 
internal,  408 
glenoid,  404 

of  fingers,  415 
hyo-epigloltic,  257 
hyoid  bone,  252 
interarticular  of  ribs,  303 
intercarpal,  412 
interclavicular,  401 
interosseous  of  forearm,  407 
inlerspinous,  297 
intertransverse,  299 
jaw, 305 

internal  lateral  of,  155 
larynx,  252 
latum  pulmonis,  173 
metacarpal,  414 
metacarpo  phalangeal,  415 
nucha.',  284,  299 
oblique  of  radius,  408 
occipito  atloid,  300 
occipito-axial,  300 
odontoid,  300 
orbicular  of  radius,  408 
palpebral,  47,  48 
palmar,  362,  412 
phalangeal  of  hand,  416 
posterior,  common,  296 


INDEX. 


425 


Ligaments  of  ■  — 

pterygo  mandibular,  53 

radio  carpal,  41 1 

ulnar,  409 

rhomboid,  401 

round  of  radius,  40S 

scapulo  clavicular,  402 

shoulder-joint,  404 

spheno-mandibular,  155,  306 

spinal,  296 

stellate,  303 

sterno-clavicular,  4 

stylo-hyoid,  156 

stylomandibular,  85,  115 

subflava,  297 

superspinous,  297 

temporomandibular,  306 

thyroarytenoid  inferior,  259 
superior,  259 

thyro  epiglottic,  256 

thyrohyoid,  253 

transverse,  of  fingers,  357 
metacarpal,  398 

trapezoid,  403 

wrist,  403,  411 

Zinn,  75 
Ligamenta  subflava,  297 

cruciata,  364 
Ligamentum  nuchae,  299 

suspensorium,  301 

vaginalia,  364 
Limbus  oculi,  76 
Linguae  fraenum,  267 

dorsalis  artery,  121. 
Lingual  artery,  112,  121 

glands,  268 

nerve,  120 
Longitudinal  sinus,  inferior,  31 

superior,  29 
Lower,  tubercle  of,  216 
Lumbar  aponeurosis,  373 

fascia,  2S5 
Lumbricales  of  hand,  365 
Lungs,  231 

air-cells  of,  235 

arteries  of,  236 

color  of,  233 

contractibility,  233 

dimensions  of,  180 

fissures  of,  232 

infundibula  of,  234 

lobes  of,  178 

lymphatics  of,  237 

nerves  of,  237 

position  and  form  of,  178 

relations  to  chest  wall,  178 

root  of,  constituents,  212 


Ligaments  of  •  — 

shape  of,  232 

structure  of,  227,  234 

veins  of,  237 

weight  of,  180 
Lunula;  of  valves,  219,  220 
Lymphatics,  axilla,  315 

heart,  223 

internal  mammary  artery  with,  172 

intercostal,  209 

lung,  237 

parotid  gland,  59 

scalp,  24 
Lymphatic  glands,  cervical,  deep,  103 

superficial,  8i 


M. 

Mammary,  internal  artery,  136,  171 
Mandibular  artery,  nerve,  36 
Marshall,  oblique  vein  of,  215,  223 
Maxillary  artery,  external,  54 

internal,  147 

nerve,  36,  269 

vein,  150 
Meatus  of  the  nose,  279 
Meckel's  ganglion,  250,  271 
Median  nerve,  335,  352 
in  palm,  363 

vein,  341 
Mediastina,  175 

anterior,  175 

middle,  176 

posterior,  176,  19S 

superior,  176 
Meibomian  glands,  47,  49 
Membrana  nictitans,  4O 

sacciformis,  41  [ 
Membrane,  costo  coracoid,  310 

cricothyroid,  254 

interosseous  of  forearm,  409 

thyrohyoid,  253 

Schneiderian,  281 
Membranes  of  brain,  26, 
Meningeal  arteries,  ^^ 

anterior,  33 

middle,  ^3,  148 

parva,  33,  149 

posterior,  23^  122 

small,  149 
Mitral  valves,  221 

middle,  cervical  ganglion,  165 
Mohrenheim's  fossa,  78 
Molar  glands,  54 
Morgagni,  sinus  of,  241 
Motor  oculi  nerve,  34,  74 


426 


INDEX. 


Mouih,  muscles  of,  41 
Movements  of  spine,  299 
Multifidus  spinae,  290 
Muscles :  — 

abductor  indicus,  39S 

minimi  digiti  manus,  362 

pollicis,  360 
accessorius  ad  sacro-lumbalem,  288 
adductor  pollicis,  361 
anconeus,  392 
aryteno-epiglottideus,  263 

inferior,  262,  265 

superior,  265 
arytenoideus,  263 
attollens  aurem,  21 
attrahens  aurem,  21 
auricularis,  391 
azygos  uvulae,  245,  246,  247 
of  back,  284,  367 
basio-glossus,  117 
biceps  of  arm,  330 
biventer  cervicis,  289 
brachialis  anticus,  332 
brachio-radialis,  347 
buccinator,  52 
cervicalis  ascendens,  288 
chondro-glossus,  117 
circumflexus,  246 
complexus,  289 
compressor  naris,  50 

sacculi  laiyngis,  262 
constrictors  of  pharynx,  239.  242 
coraco-brachialis,  331 
comigator  supercilii,  45 
crico-arytenoideus  lateralis,  263 

posticus,  261-262 
cricothyroideus,  262 
cutaneous,  79 
deltoid,  378 
depressor  alas  nasi.  51 

septi  narium  of  Hallac,  42 

anguli  oris,  42 

labii  inferioris,  42 
digastric,  107 
dilatator  naris  anterior,  51 

posterior,  51 
erector  spinae,  287 
extensor  carpi  radialis  brevior.  390, 

393 

longior.  390 
carpi  ulnaris,  392 
communis  digiiorum,  390 
indicis,  395 
longus  digitorum.  393 
minimi  digiti,  391 
ossis  met.  pollicis,  393 
primi  internodii  pollicis,  393 


Muscles :  — 

extensor  secundi  internodii  pollicis, 

394 
flexor  brevis  minimi  digili  manus, 
362 

pollicis,  361 

carpi  radialis,  343 
ulnaris,  345 

pollicis,  353 

profundus  digitorum,  353 

sublimis  digitonim,  345 
Forbes',  182 
genio  hyoglossus,  118 

hyoideus,  116 
Hilton's,  262 
hyoglossus,  117 
hyoid  region,  95 
ilio-costalis,  288 
indicator,  395 

inferior  constrictor  of  pharynx,  240 
infracostal,  205 
infra-hyoid  region,  95 
infra-spinatus,  381 
intercostal,  external,  205 

internal,  205 
interosseous  of  hand,  398 

palmar,  399 
interspinales,  291 
intertransversales,  291 
kerato  glossus,  117 
latissimus  dorsi,  323,  370 
levator  anguli  oris,  52 
scapulae,  374 

glandular  thyroides,  102 

labii  inferioris,  42 

superioris  alaeque  nasi,  52 
proprius,  52 

menti,  42 

palati,  246 

palpebrcE,  47,  65,  68 

uvulae,  246,  247 
levatores  coslarum,  290 
lingualis,  inferior,  268 

superficial,  268 
longissimus  dorsi,  288 
longus  colli,  295 
lumbricales  manus,  365 
masseter,  143 
of  mastication,  143 
middle  constrictor  of  pharynx.  239 
mouth,  41 

mullifidus  spinae,  290 
musculus  risorius,  79 
mylo-liyoideus,  1 15 
naso-labialis,  42 
nose,  of  tlie,  49 
obliquus  inferior  oculi,  65,  77 


INDEX. 


427 


Muscles  :  — 

obliquus  inferior  capitis,  291 

superior  oculi,  65,  69 
capitis,  291 
occipito-frontalis,  20 
opponens  digiti  minimi,  362 
opponens  pollicis,  361 
orbicularis  oris,  41 

palpebrarum,  44 
omohyoid,  92,  375 

relations  of,  93 
palatoglossus,  245,  248 

pharyngeus,  246,  248, 250 
palmaris  brevis,  79,  356 

longus,  345 
pectoralis  major,  309 

minor,  316 
pharyngeal,  239-242 
platysma  myoides,  79,  80,  308 
prevertebral,  294 
pronator  quadratus,  353 

radii  teres,  343 
pterygoideus  externus,  145 

internus,  146 
pyramidalis  nasi,  50 
quadratus  menti,  42 
recti  of  the  eye,  65,  75 
rectus,  capitis  anticus  major,  296 
minor,  296 

lateralis,  292 

posticus  major,  291 
minor,  291 

externus  oculi,  75 

internus  oculi,  76 

inferior  oculi,  76 

sternalis,  310 

superior  oculi,  69 
retrahens  aurem,  21 
rhomboideus  major,  374 

minor,  374 
risorius,  41 
rotatores  spinae,  290 
salpingo-pharyngeus,  243 
sacrolumbalis,  288 
of  Santorini,  41 
scalenus  anticus,  125 

medius,   125 

posticus,  125 
semi-spinalis  colli,  290 

dorsi,  290 
serratus  magnus,  325,  376 

posticus  inferior,  284 
superior,  2S4 
spinalis  dorsi,  2S9 
splenius  capitis,  287 

colli,  287,  289 
sterno-cleido  mastoideus,  86 


Muscles  :  — 

sterno-hyoid,  91 
thyroid,  92 

styloglossus,  118,  155 
hyoideus,  108 
pharyngeus,  155,  242 

subanconeus,  385 

subclavius,  31 1 

subcostal,  205 

sublimis  digitorum,  345 

subscapularis,  325,  382 

superior    constrictor    of    pharynx, 

supinator  radii  brevis,  395 

longus,  347 
supraspinales,  290 
supraspinatus,  382 
temporal,  144 
tensor  palati,  246 

tarsi,  49 
teres  major,  323,  382 

minor,  382 
thyroarytenoideus,  264 

epiglottideus,  265 

hyoid,  93 
tracheal,  230 
trachelo-mastoid,  288 
transversalis  colli,  288 
transverso-spinalis,  290 
trapezius,  368 
triangularis  sterni,  171 
triceps  extensor  cubiti,  339,  385 
uvuliloe  ozygos,  245,  246 
zygomaticus  major,  42 

minor,  42 
Musculi  papillares,  217,  221 
pectinati,  214,  216,  220 
Musculo-cutaneous  nerve,  336,  341 
Musculo-spiral  nerve,  340 
musculus  ciliaris,  45 
Mylo  hyoid  artery,  149 

nerve,  115,  153 


N. 


Nasal  fossas,  posterior  openings,  243 

boundaries,  279 

duct,  280 

muscles,  49 
Nasion,  25 

Naso-lobular  nerve,  51,  62,  71 
Neck,  central  line  of,  93,  105 

cutaneous  nerves  of,  81 

dissection  of,  78 

lymphatics  of,  81 

surface  marking  of,  78 


428 


INDEX. 


Neck,  triangles  of,  87 

anterior,  87 

carotid  inferior,  91 
superior,  91 

digastric,  106 

posterior,  87 

submandibular,  106 

supra-clavicular,  83 
Nerves :  — 

abducens,  36,  75 
abducens  oculi,  75 
acromial,  82,  308 
ansa  hypoglossi,  124 
Arnold's,  24,  160 
auditory,  36 
auriculo-parotidean,  82 

temporal,  142,  153 
auricular,  60 

auricular  branch  of  pneumogastric, 
24,  160 

posterior,  123 

great,  82 
axillary  plexus,  321 
back,  cutaneous  of,  292,  367 
Bell,  nerve  of,  325,  377 
brachial  plexus,  137,  321 
buccal  branch  of  facial,  62 

mandibular,  152 
cardiac  branch  of  pneumogastric, 
162,  203 

inferior,  167 

middle,  167 

superior,  167 
carotid  of  glossopharyngeal,    157, 
269 

sphenopalatine  ganglion,  269 
cervical,  acromial  branch  of,  82, 308 

posterior  branches  of,  368 

supei-ficial,  82 

plexus,  deep,  124 
cervico-facial,  60,  61 
chorda  tympani,  154,  276 
ciliary,  long,  71,  74 

short,  74 
circumflex,  322,  382 
clavicular,  82,  308 
coccygeal,  294 

posterior  branch  of,  368 
communicans  hypoglossi,  95,  100, 

124 
coronary,  anterior,  212 

posterior,  212 
cranial,  exit  of,  34 

at  base  of  skull,  271 
cutaneous  of  chest,  308 

forearm,  328,  341,  387 

neck,  81 


Nerves :  — 

dental,  anterior,  270 

inferior,  153 

posterior,  270 
descendens  hypoglossi,  95, 100,  119 
dorsal,  292,  367 
dura,  26 

eighth  cranial,  36 
eleventh  cranial,  37,  162 
external    cutaneous,    of    musculo- 

spiral,  340,  384 
facial,  36,  40,  59 

cervical  branch  of,  82 

in  skull,  275 
fifth  cranial,  35,  65 
first  cranial,  34,  283 
fourth  cranial,  34,  64,  65,  67 
frontal,  64,  66 

ganglion  of  Ehrenritter,  157 
glosso-pharyngeal,  36,  156,  269 

carotid  branches  of,  157,  274 

lingual  branches  of,  157 

pharyngeal  branches  of,  157 

tonsillar,  157 
great  auricular,  58 

occipital,  24,  291 
gustatory,  120,  154,  269 
hypoglossal,  37,  118,  163 
incisor,  153 
inferior  dental,  1 53 

laryngeal  or  recurrent,  203 
infra-maxillary  of  facial,  62 

orbital  of  facial,  60 
of  maxillary,  63 

trochlear,  62,  70,  71 
intercostal,  208 

abdominal,  208 

anterior   cutaneous   branches, 
208, 308 
intercosto-humeral,  314,  326,  385 

lateral,  cutaneous  of,  308 

pectoral,  208 
internal    cutaneous,    of   arm,   308, 

326 
interosseous  anterior,  352,  355 

posterior,  396 
Jacobson's  or  tympanic,  274 
jugular  ganglion,  157 
labial,  62,  153 
lachrymal,  64,  66 
laryngeal,  external,  in,  160 

inferior,  162,  203,  265 

inferior  or  recurrent,  162,  203, 
266 

internal,  iii,  162 

recurrent,  162,  203,  265 

superior,  in,  162,  265 


INDEX. 


429 


Nerves :  — 

lesser  cutaneous,  of  arm,  327 
lingual,  120,  154 

of  glossopharyngeal,  151 
longus  colli,  139 
lumbar,  294 

posterior  branches  of,  36S 
malar  branch  of  maxillary,  63,  77 
malar,  of  facial,  60 
mandibular,  36,  150,  306 
maxillary,  36,  269 

orbital  branch  of,  77 
median,  335,  352 

cutaneous  branch  of,  352 

digital  branches  of,  363 

in  the  palm,  356,  363 
mental,  63,  153 
masseteric,  151 
motor  oculi,  34,  74 
musculocutaneous,  of  arm.  336,  344 

spiral,  340,  384 
mylo  hyoid,  153 

hyoidean,  1 15 
nasal,  66,  70,  283 

septal  branch  of,  71 

superior,  272 

upper,  272 
nasolobular,  51,63,  71 

palatine,  272,  283 
neck,  cutaneous  of,  81 
nervi  molles,  56         ' 
ninth  cranial,  36,  274 
noni  communicantes,  100,  124 
Obersteiner  filaments  of  spinal  ac 

cessory, 
occipital  of  facial,  60 

great,  24,  291 

small,  24,  82 
oesophageal    plexus,   anterior   and 

posterior,  160 
olfactory,  34,  283 
ophthalmic,  36,  66 
optic,  34,  65,  71 

orbital    branch  of   superior  maxil 
lary,  62,  77 

malar  branch  of,  77 
palatine,  anterior,  272 

external,  272 

nasal  branches  of,  272 

naso-,  272 

posterior,  272 
palpebral,  62 

palmar  branch  of  median,  356,  363 
perferous  Casseri,  336 

of  ulnar,  359,  367,  400 
respiratory,  of  Bell,  325 
superficial  petrosal,  40,  276 


Nerves:  — 

pes  anserinus,  40,  58,  60 
petrosal,  external,  40,  276 

great,  40,  272,  276 

small,  superficial,  40,  276 
petrous  ganglion,  157 
pharyngeal,  272 

of  glossopharyngeal,  157 

of  pneumogastric,  160 

pharyngeal  plexus  of,  162 
phrenic,  124,  127 

in  chest,  197 
pneumogastric,  37,  97,  159,  203,  275 

auricular  branch  of,  24,  275 

in  the  chest,  204 

course  of,  203 
portio  dura,  40,  60 
position  of,  in  sphenoidal  fissure,  38 
posterior  auricular,  24,  60 

branches  of  spinal,  292 

interosseous,  340,  396 

scapular,  375 

thoracic,  139,  325 
pterygoid,  151 
pulmonary   branches   of    pneumo 

gastric,  203,  237 
radial,  340,  349,  387 
recurrent  or  inferior  laryngeal,  162, 

203 
respiratory  (external),  of  Bell,  139, 

325-  377 
rhomboid,  139 
sacral,  294 

plexus,  posterior  branches  of, 

369 
scaleni,  139 
scalp,  of,  22 
second  cranial,  34,  7 1 

cervical,  277,  292 
sensory  nerves  of  face,  62 
seventh  cranial,  36,  60,  275 
shoulder,  cutaneous  of,  377 
sixth  cranial,  36,  65,  75 
small  occipital,  24,  82 

superficial  petrosal,  40,  276 
in  sphenoidal  fissure,  38 
sphenoethmoidal,  73 
spinal    accessory    portion,    37,  89, 

162,163,373 
spinal,  posterior  branches  of,  292, 

368 
splanchnic,  great,  204 

lesser,  204 

smallest,  204 
sternal,  82,  308 
subclavius,  138 
suboccipital,  277,  292 


430 


INDEX. 


Nerves : 

suboccipital,  cutaneous  bianch   of, 

24 
subscapular,  322 
supra  claviciilar,  82,  308 

maxillary  branch  of  facial,  62 

orbital,  23,  62,  66 

scapular,  139,  375,  383 

trochlear,  23,  62,  66 
sympathetic,  cervical,  164 

in  the  chest,  204 

in  the  orbit,  65 
temporal  branch  of  maxillary,  23, 
63.  77 

deep  anterior,  151 
posterior,  151 

branches  of  facial,  24,  60 

middle,  151 
temporo-facial,  24,  60 

malar,  23,  63 
tenth  cranial,  37,  159,  203,  275 
third  cranial,  34,  65,  74 
thoracic  anterior,  140,  207,  312 

posterior,  139,  207,  368,  325 
tonsillar  of  glosso-pharyngeal,  157 
trifacial,  35 

trochlear,  of  orbit,  66,  70 
trochlearis,  34 
twelfth  cranial,  37,  118,  163 
tympanic,  274 
ul'iar,  333,  338,351 

deep  palmar  branch  of.  367 

dorsal,  cutaneous  of,  387 

in  the  palm,  359,  400 
deep,  367 
Vidian,  272,  283 
Wrisberg,  140,  312,  327,  384 
Nei"vi  molles,  56 
Nose,  arteries  of,  54,  278,  283 
cartilages  of,  278 
dissection  of,  278 
interior  of,  278 
meatus  of,  279 
mucous  membrane  of.  281 
muscles  of,  49 
nerves.of,  278,  283 
septum  of,  278 
veins  of,  283 


O. 

Obelion,  25 

Obliquus  inferior,  69,  77,  291 

superior,  69,  292 
Occipital  artery,  21,  122,  294 

point,  25 


Occipital  sinus,  23 

nerve,  great,  24,  291 
small,  24,  81 

vein,  22,  123 
Occipito-atloid  ligaments,  300 

axial  ligaments,  300 

frontalis,  20 
Odontoid  ligaments,  300 
Oculi  tendo,  43 

tutamina,  45 
Oesophageal  arteries,  202,  209 

glands,  203 

plexus,  202 
Oesophagus,  201 

relations  of,  201 

structure  of,  202 
Olfactory  bulb,  34 

cells,  283 

nerves,  283 
Openings  of  heart,  217 

upper,  of  thorax,  168 
Ophthalmic  artery,  72,  277 

ganglion,  73 

nerve,  36,  66 

veins,  73 
Ophryon,  25 
Opisthion,  25 
Optic  nerve,  34,  65,  71 
Orbicularis  oris,  41 

palpebrarum,  44 
Orbit,  dissection  of,  63 

contents  of,  65 

fascia  of,  64 

nerves  at  back  of.  40 

periosteum  of,  64 
Os  hyoides,  252 
Otic  ganglion,  272 

branches  of.  272 


Pacchionian  bodies,  28 
Palate,  glands  of,  250 

hard,  250 
Palate,  pillars  of,  245 

soft,  244 

muscles  of,  246 
Palati  circumflexus,  246 

levator,  246 

tensor,  246 

velum  pendulum,  244 
Palatine  artery,  ascending,  115 

descending,  150 
Palmar  arch,  deep,  367 

fascia,  356 

superficial,  357 


INDEX. 


431 


Palmar  profunda  artery,  366 
I'alpebra?,  47 

cartilages  of,  4S 

conjunctiva  of,  47 
Panniculus  carnosus,  79 
Papilla  lachrynialis,  46 
Papillae  circumvallatae,  267 

filiformes,  268 

fungiformes,  267 
Parotid  gland,  57 

duct,  59 

relations  of,  57 

structure  of,  57 

structures  in,  58 
Parotid's  glandula  socia,  59 
Pecquet,  cistern  of,  200 
Pericardium,  1S2 

objects  seen  on  opening,  1S8 

structure  of,  182 

vestigial  fold  of,  183 
Pes  anserinus,  40,  59,  60 
Petit,  triangle  of,  373 
Petrosal  ganglion,  274 

nerve,  lesser,  40,  272 

superficial  external,  40 

small,  276 

great,  40,  272,  276 

sinuses,  inferior,  ;}^ 
superior,  33 
Pharyngeal  aponeurosis,  239,  242 

artery,  ascending,  123,  158 
Pharyngeal  fascia,  239 

tonsil,  243 

veins,  124 

venous  plexus,  239 
Pharynx,  237 

constrictors  of,  239 

mucous  membrane  of,  243 

openings  into,  242 
Phrenic  nerve,  124,  127 

in  chest,  197 

differences  of,  197 
Pisiform  bone,  412 
Pituitary  body,  277 
Platysma  myoides,  80,  30S 
Plexus,  brachial,  137,  321 

cardiac    de:)p,  203,  210,  211 
superficial,  204,  211 

carotid,  39,  165 

cavernous,  40,  165 

cervical,  superficial,  82 
deep,  124,  370 
posterior,  292 

coronary,  anterior,  212 
posterior,  212 

gulae,  203 

infra-orbital,  6i 


Plexus,  oesophageal,  159,  204 

pharyngeal,  239 

pterygoid,  149 

pulmonary,  204,  237 

superficial  cardiac,  211 

sympathetic  of  abdomen,  205 
Pleura,  173 

outlines  of,  173 

cavity  of,  173 
Plica  semilunaris,  46 
Pneumogastric  nerve,  37,  159,  275 
in  chest,  203,  204 

ganglia  of,  275 

auricular  branch  of,  24 
Points  of  surgical  interest,  24 
Pomum  Adami,  253 
Portio  dura,  40,  59 
Portis  intermedia  of  Wrisberg,  36 
Pouches,  laryngeal,  262 
Precordial  region,  180 
Prevertebral  muscles,  294 

fascia,  84 
Pterion,  25 
Pterygo  palatine  artery,  150 

mandibular  ligament,  53 
region,  140,  145 
Ptosis,  74 
Pulmonary  artery,  209,  236 

nerves  of  pneumogastric,  203,  237 

valves,  218 
Pulmonis  hilum,  178 
Puncta  lachrymalia,  46,  48 

R. 

Radial  artery,  347 

at  back  of  wrist,  397 
in  palm  of  hand,  366 

nerve,  340,  349,  387 

vein,  328,  341 
Ranine  arteiy,  121 

vein,  1 2 1 
Ranula,  155 

Receptaculum  ch.yli,  200 
Region,  precordial,  180 
Retina,  arteria  centralis  of,  72 
Ribs,  movements  of,  305 
Rima  glottidis,  259 
Ring,  fibrous,  of  heart,  223 
Rivinus,  ducts  of,  119 

S. 

Sac,  lachrymal,  48,  280 
Sacculus  laryngis,  259,  262 
Sacro-lumbalis,  288 
Santorini,  muscle  of,  41 


432 


INDEX. 


Scaleni  muscles,  125 
Scalp,  disseclioii  of,  19 

arteries  of,  21 

lymphatics  of,  24 

neiA'es  of,  22 

veins  of,  22,  28 
Scapulas  artei"y,  dorsalis,  319 
Scapular  artery,  posterior,  135,  376 
supra',  135,375.  3S4 

vein,  posterior,  136 
Schneiderian  membrane,  2S1 
Semilunar  fascia,  328 

valves,  218 
Semispinalis  colli,  290 

dorsi,  290 
Sensory  nerves  of  face,  62 
Septum,  artery  of  nasal,  56 

auricularum,  214 

narium,  27S 

tongue,  269 
Serratus  magnus,  325,  376 

posticus  inferior,  284 
superior,  284 
Seventh  cranial  nerve,  36,  60,  275 
Sheath,  axillary  vessels,  211 
Sheaths  for  extensor  tendons  of  hand, 

388 
Sheaths  for  flexor  tendons  of  hand,  364 
Shoulder,  cutaneous  nerves  of,  377 

joint,  404 

movements  of,  406 

synovial  membrane  of,  406 

muscles  in  relation  with,  406 
Sinus  coronary,  214,  215 

Morgagni,  241 

venous,  cavernous,  32,  37 

circular,  32 

coronary  of  heart,  214,  222 

dura,  29 

lateral,  31 

longitudinal,  inferior,  31 
superior,  29 

occipital,  33 

petrosal,  inferior,  ^^ 
superior,  ^3 

straight,  31 

transverse,  2;^ 

venosus,  214,  220 
Sinuses,  great,  of  aoita,  194 

Valsalva,  194,  219 
Sixth  cranial  nerve,  36,  75 
Socia  pavotidis,  glandula,  59 
Space,  interpleural,  175 

Meckel's,  27 

subdural,  26 
Sphenoidal    fissure,  structures   passing 
through,  38 


Sphenopalatine  artery,  150 

ganglion,  270 

branches  of,  271 
Spince  rotatores,  290 
Spinal-accessory  nerve,  37,  89,  162,373 

lateral  artery  from  vertebral,  134 
Spine,  ligaments  of,  296 

movements  of,  299 
Splanchnic  nerves,  204 

great,  204 

lesser,  204 

smallest,  204 
Splenius  capitis,  287 

colli,  287 
Stenon's  duct,  59 
Stephanion,  25 
Sterno-mastoid  muscle,  87 

artery,  middle,  87,  135,  375 
superior,  122 

parts  beneath,  94 
Straight  sinus,  31 
Stylo-glossus,  118,  155 

pharyngeus,  155,  242 
Stylo-hyoid  ligament,  156 

muscle,  108 
Stylomandibular  ligament,  85,  115 
Subclavian  artery,  left,  130,  196 

right,  127 

ligature  of,  132 

triangle,  89 

vein,  137 
Subdural  space,  26 
Sublingual  artery,  121 

gland,  1 19 
Suboccipital  nerve,  277,  292 

triangle,  292 
Submaxillary,  or  mandibular  ganglion, 
120 

gland,  109 

triangle,  306 

subdural  space,  26 

subnasal,  26 
Subscapular  artery,  319,  375 

nerves,  322 
Subscapularis,  325,  382 
Supra  clavicular  nerves,  89 

triangle,  89 
Supra  hyoid  aponeurosis,  108 
Supra  orbital  artery,  21,  73 

nerve,  23,  62,  66 
Supra-scapular  artery,  135,  383 

nerve,  139,  375.  3^3 

vein,  136 
Supra-trochlear  nerve,  23,  62,  66 
Supra-spinales,  290 
Supra-spinatus,  382 
Supra  spinous  ligament,  297 


INDEX. 


433 


Surgical  points  of  interest  in  scalp,  24 
Surface  marking  of  the  neck,  78 

of  the  arm,  307 

cervical,  164 
Sympathetic  nerves : 

cranial,  165 

nervi  moUes,  56 

in  orbit,  65 

thoracic,  204 


T. 


Tarsal  cartilages  and  ligaments,  47 
Temporal  artery,  141 

superficial,  22,  142 

deep,  149 

fascia,  143 

muscle,  144 

nerves,  deep,  151 

veins,  142 

superficial,  22,  142 
Tempore  fascial  nerve,  60 
Temporo  mandibular  ligaments,  306 
Tendo  palpebrarum,  43 
Tendons,  flexor  of  hand,  363 

extensor,  388 
Tenon,  capsule  of,  64,  76 
Tenth  cranial  nerve,  37,  203,  275 
Tentorium,  28 
Teres  major,  323,  382 

minor,  382 
Thebesii  foramina,  214 

valve,  215,  223 

veins  of,  223 
Theca,  364 
Thena,  355 

Third  cranial  nerve,  34,  65,  74 
Thoracic  aorta,  descending,  19S 

artery,  alar,  316,  319 
long,  319 
superior,  311,  319 

nerves,  anterior,  207,  312 

posterior,  139,  207.  325,  368 
Thoracic  duct,  200 
Thoracico-acromialis  artery,  312,  319 
Thorax,  base  of,  167 

dissection  of,  169 

osseous  measurements.  168 

upper  openings  of.  168 

topography  of  viscera  of,  1S4.  185, 
186.  187 
Thymus  gland,  169,  175 
Thyro-arytenoideus,  264 
Thyro  epiglottideus,  265 
Thyrohyoid,  93 
Thyroid  artery,  superior,  1 1 1 


Thyroid  body,  loi 

inferior,  135 

vein,  1 1  [ 

cartilage,  253 

gland, 102 

isthmus,  loi 

arteries  of,  102 

lymphatics  of,  103 

pyramid  of,  io2 
Thyroid,  nerves  of,  103 

structure  of,  103 

veins  of,  102 
Tongue,  1 16,  266 

arteries  of,  269 

dorsum,  267 

foramen  caecum  of,  267 

fraenum,  267 

glands  beneath,  268 

mucous  membrane  of,  267 

muscular  fibres  of,  26S 

nerves  of,  269 

papillas  of,  267 

raphe  of,  267 

septum  of,  269 
Tonsillar  artery,  114 
Tonsils,  248 

pharyngeal,  243 
Torcular,  29 
Trachea,  228 

cartilages  of,  229 

elastic  tissue,  230 

glands  of,  230 

mucous  membrane  of,  230 

muscular  fibres  of,  230 

relations  of,  228 
Tracheotomy,  surgical  relations  of,  105 
Transverse  sinus.  ;^;^ 
Trapezius,  368 
Triangle,  carotid  inferior,  91 
superior,  91 

diagastric,  106 

elbow,  343 

infraclavicular,  310 

neck,  anterior,  90 
posterior,  89 

occipital,  89 

Petits,  373 

subclavian,  89 

submandibular,  106 

suboccipital,  292 

supraclavicular,  89 
Triangularis  sterni,  171 
Triceps  extensor  cubiti,  339,  385 
Tricuspid  valves,  170,  217 
Trifacial  nerve.  35 
Trochlea  of  orbit,  69 
Trochlearis  nerve,  34 


434 


INDEX. 


Tube,  Eustachian,  250 
Tubes,  bronchial,  21:9 
Tutamina  oculi,  45 
Twelfth  cranial  nerve,  37,  118,  163 
Tympanic  nerve  of  facial,  274 
glossopharyngeal,  274 


U. 

Ulnar  artery,  349 

nerve,  333,  338,351 
in  palm,  359,  400 
deep  in  hand,  367,  387 
veins,  32S,  341 
Uvula  of,  palate,  244,  245 
Uvulae  azygos,  246,  247 


V. 


Vagus  nerve,  37,  159,  203 
Vallum  af  tongue,  267 
Valsalva,  sinuses  of,  194,  221 
Valve,  coronary,  214 

Eustachian,  214,  215 

Hasner,  280 

Thebesius,  215,  223 
Valves,  cardiac,    position    of,    169-171, 
189 

aortic,  170 

auscultation  of,  181 

mitral,  170,  221 

pulmonary,  169,  218 

semilunar,  218 

tricuspid.  170,  217 
Veins :  — 

angular,  56 

auricular,  123 

axillary,  320 

azygos,  left  upper,  200 
major,  199 
minor,  200 

right,  192 

basilic,  328 

median,  328,  341 

brachial,  335 

brachiocephalic,  190 

bronchial,  237 

cardiac,  anterior,  223 
great,  222 
posterior,  222 

cava,  inferior,  214 

superior,  191,  214 

cephalic,  310,  312,  328 
median.  328,  341 

coronary,  of  heart,  222 


Veins :  — 

elbow,  in  front  of,  135,  328 
facial,  56,  109 
frontal.  22 
of  Galen,  216 
innominate,  190 
intercostal,  superior,  136,  191 
jugular  anterior,  81 
external,  58,  80 
internal,  99 
posterior  external,  81 
maxillary  internal,  58,  150 
median,  341 

deep,  341 
nasal,  283 

oblique,  of  Marshall,  215,  223 
occipital,  122 
ophthalmic,  73 
inferior,  73 
pharyngeal,  124 
pterygoid  plexus  of  veins,  150 
radial,  328,  341 
ranine,  121 
scalp,  of,  22 
scapular  posterior,  136 

supra,  136 
subclavian,  137 
superior  cava,  191 
supra-orbital,  22,  56 

scapular,  136 
temporal,  58,  142 

superficial,  22 
Thebesii,  216,  223 
thyroid  superior,  i  t  i 
ulnar  anterior,  328,  341 
posterior  328,  341 
umbilical,  226 
vertebral,  134 
pendulum  palati,  244 
Ventricle  of  heart,  left,  221 
right,  216 
muscular  fibres,  224 
Ventricle  of  larynx,  261 
Ventricular  bands,  259 
Vertebral  aponeurosis,  284,  373 

artery,  ^3'  ^94 
Vestigal  fold  of  pericardium,  183 
Vibrissa,  282 
Vidian  artery,  150 

nerve,  272,  283 
Vincula  tendinum,  365 
Viscera  of   thorax  and  abdomen,   184, 
185,  186,  187 
ventral  topography  of,  184 
dorsal  topography  of,  185 
right,  lateral  topography  of,  186 
left,  lateral  topography  of,  187 


INDEX. 


435 


Vocal  cords,  inferior  or  true,  259 
superior  or  false,  25S 
bands,  259 

Wharton's  duct,  154 
Willis,  cords  of,  30 
Wrisberg,  cartilages  of,  256 
ganglion  of,  211 


Wrisberg,  nerve  of,  312,  327,  384 
Wrist-joint,  synovial  membranes  of,  414 

triangular  fibiocartilage  of,  410 
Wry-neck,  87 


Zinn,  ligament  of,  75 
Zygomaticus  major,  42 
minor,  42 


^ 

^ 


.VERSITYLIBRARItbinsl.Stx) 

QIV134H71  1901C.1V.1 

Hn!,'. 


2002157411 


^  / 


